Security Features in World Banknotes
Ever since banknotes have been used they have undergone change. One has only to look through any reference book on banknotes to see that for any one country, or for any one issuing authority, there has been issue after issue wherein the banknotes have undergone transformation.
The transformation may be minor or it may be dramatic. The reasons for change are many—governments change, and introduce their own currency; the currency changes (e.g. from pounds to dollars); inflation often brings new issues; and most importantly there is a continuing need for the issuing authorities to keep one step ahead of the forgers. The continuing struggle of the note issuing authorities and the security printers to keep the counterfeiters at bay is the subject of this article.
There have been many security features come and go since paper money was first introduced and the study of these features can be very rewarding. Some of the features mentioned here are quite well-known, whilst others will be new to some collectors. So let us take a wander through the years and study the many devices and innovations that have been produced in an effort to deter and defeat the forgers.
From the very beginning, note issuing authorities have realised the need to use special materials in the production of paper money. The use of special materials for paper money is twofold—firstly there is the need to produce paper that is long lasting, and secondly there is a desire to use a type of paper which is not readily available to the public.
The first issue of paper money was in 7th century China, and the circulation of paper money in China continued for many centuries. These early notes are often called “Ming” notes because most of the surviving notes were issued during the Ming dynasty. The notes were printed on paper that was especially manufactured from mulberry bark, as opposed to the more common paper which was manufactured from bamboo. The government in China became so possessive about the manufacture of mulberry bark paper that it took over the mills that produced it and forbade the private dealing of the paper.
The first banknotes that were issued in Europe were those of the “Stockholms Banco” of Sweden and these notes were printed on white rag paper. Exactly what the rags were made of is unknown, however it was probably linen, as linen rag paper became the standard material for banknotes throughout Europe in the 18th century.
The Bank of England “white” notes were printed on paper made from linen, but when the Nazis tried to counterfeit these notes during the second world war, they found that they couldn’t reproduce the correct colour. However, they soon discovered the answer - the linen used for the English notes was made from old linen and not new linen, as they had originally supposed. The truth was that the English notes were being produced from old mail bags. Until the issue of these forgeries, the “quality” of the paper used in English notes was regarded by the Bank of England as one of the main security features of the notes.
Most modern notes use cotton rag fibre. Portals, who supply banknote paper for the notes of over one hundred countries, use cotton rag fibre; whilst Cranes, who supply the paper for U.S. banknotes uses a mixture of cotton, linen and sometimes denim. In 1985 the Canadian notes changed from a paper with a 25% flax (linen) content to a total cotton content.
Paper produced from linen and cotton has several features which make it different to paper manufactured from timber pulp. The texture of the note is the most noticeable quality, whilst the strength and ability to wear are features which make it attractive to note issuing authorities. From the point of view of security, there is also another special quality - the lack of fluorescence. Most paper manufactured from timber pulp, or from a mixture of timber pulp and cotton fibre, will fluoresce (glow a brighter white) when submitted to ultraviolet light, whilst paper made from cotton or linen will remain stable.
Notes issued on plain paper are often found in emergency issues, as necessity overcomes the desire for a long wearing medium. An example of plain paper being used for banknote production can be found in the first issue of the Republic of Biafra.
Cotton and linen are not the only medium used in the production of banknotes - occasionally more obscure materials are used. One of the stranger materials used for issuing banknotes was sheepskin, which was used for one of the issues of the Cocos-Keeling Islands. The skin was processed to become stiff, even though the leather was quite thin, and to the casual observer would not be recognised as leather.
There have also been a couple of moves away from paper into the use of plastics. The first issue to be printed on plastic came from Haiti, who issued a series of “Tyvek” plastic notes in the early 1980’s. Shortly after (in 1983) there were issues from Costa Rica and the Isle of Man with the same material. However, this experiment proved unsatisfactory, as it was found that the printing lifted from the body of the note, and the various authorities reverted to the use of paper.
Australia is currently issuing a series of plastic notes following the development of a new plastic by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Note Printing Australia. Whilst they have had some initial problems both with the notes and with public acceptance, the issue is set to continue.
Watermarks were used in paper manufacture long before the the issue of the first banknotes in Europe. The first specific watermark for a banknote was that of the 1661 issue of the Stockholms Banco, wherein the word “BANCO” appeared in a scroll. From thenceforth watermarks became a standard security feature of banknotes.
The watermark is introduced at the time of paper manufacture, and was originally produced by raised images in the paper moulds which impressed the image of the watermark into the paper, thus affecting the moisture levels in the paper during the drying process, which is what gives the watermark its peculiar qualities. Attempts to forge watermarks can be made by either photography or by use of a press.
However the peculiarities of a genuine watermark lie in the different shades produced by the varying thickness of paper, and when immersed in water, the watermark becomes more distinct. When a note with a false watermark, created by a press, is placed in water, the fibre in the paper swells to the same thickness and the false watermark is lost.
When a genuinely watermarked paper is held to the light, the thicker parts of the paper appear dark, and when placed beneath a light the dark parts appear lighter. A pressed or photographed watermark will not sustain these qualities.
Whilst the watermark has essentially remained the same, there have been a number of developments in the manufacture of watermarks over the years. The most notable development was the “shaded” watermark which was developed by the French company of Johannot of Annonay. The shaded watermark, which was more difficult to reproduce than the simple line watermarks which had been used until that time, appeared in the Bank of England white notes after 1855 and subsequently in many other issues from many countries.
Early watermarks for banknotes were specifically designed to suit individual notes. This practice is still wide spread, and can be seen to perfection in the watermarks of the Bank of England white notes, or in the banknotes of the Bank of Scotland prior to 1960.
Some of the individual watermarks are works of art in themselves, and the watermark of a complex Celtic pattern that appeared on the higher denomination notes of the Bank of Scotland until the middle of this century was so highly regarded that it had a patent taken out on it. Until the early part of the century, this patent was noted by the inscription “RD. NO. 18970” in the bottom margin of the notes.
With the use of sheets of paper to print many notes, there became a cost efficient need to eliminate the “lining up” of the watermark prior to printing. This has been achieved by using a watermark evenly distributed over the entire sheet, or by producing a continuous (or banded) watermark.
The watermark on the lower denomination Australian decimal notes were note specific; that is, there was one image of Captain Cook on each note. With the fifty dollar note, the image of Captain Cook is repeated the full height of the note—it is a continuous watermark. “All over” watermarks are the cheapest alternative and can be seen on many issues, including the 1949 issue of the Netherlands, the current issues of the Bank of Scotland, and in the notes of the Faeroe Islands, to name just a few.
Despite the use of watermarks that cover the entire sheet of paper and continuous watermarks, many issuing authorities still prefer note specific watermarks.
Whilst the new plastic notes produced by Note Printing Australia don’t have watermarks, they have managed to create a very similar device by setting an image into one of the polymer substrata during manufacture. In the $10 bicentennial note this image is a wave pattern in the top right quadrant of the note, and in the new $5 note it is Australia’s coat of arms in the top left of the note. This image can be clearly seen when held to the light, and faintly seen when held beneath a strong light.
The third issue of the Stockholms Banco in 1666 was issued with specific security measures, as their first two issues had been forged. Apart from the watermark which was mentioned above, each note also had eleven wax seals.
The seals were created by embossing with steel dies, then filling the back of the embossing with red sealing wax and covering the wax with paper wafers. Whilst the process seems complicated, there are no recorded forgeries of this series.
Although the use of wax seals in banknotes did not continue, the use of embossing did. The very first issue of the Bank of Scotland had the bank’s seal embossed on them, and they continued with this practice for a number of issues.
Many notes used embossed stamps, which are also known as “blind” stamps, and this device is probably best seen to advantage in the “Assignats” of republican France, although many other early European notes also used the device.
Whilst embossing was common in the 17th and 18th centuries, it appears to have lost its popularity during the 19th century. However there were some modern notes that continued the tradition, with the 1939 10,000 kronor of Sweden being a fine example.
Recent developments have seen the re-emergence of embossing in a most unlikely quarter, with some notes of the Netherlands, Singapore and Israel carry embossed or raised markings for identification by the blind or visually impaired, although these should not be considered as security features.
Many banknotes of the 18th and 19th centuries were bound in books, and presented in a manner which is similar to the modern cheque book. When a banknote was issued, it was removed from the book in much the same way that a cheque is removed from a cheque book; but whilst the cheque is detached from the “butt” by tearing perforations, the banknote was removed by cutting it away from its “counterfoil”.
The cut was usually made along a decorative panel and quite often it was an irregular cut. When the note was returned to the bank for payment, the teller could retrieve the book of counterfoils by reference to the serial number and then match the irregular edge of the banknote to its counterfoil. The genuine note would have an edge that complemented its counterfoil.
Whilst the use of counterfoils has long disappeared, many banknote designs of the 20th century continue to incorporate a panel on the left of the note which is reminiscent of the panels originally designed for use in counterfoils, such as is seen in the designs of Scotland’s British Linen Bank. The broad border at the left side of the Australian decimal notes and past issues of the Deutches Bundesbank, are also reminiscent of the use of the counterfoil.
Experiments with embedded material have been going on for many years, and one early attempt to embed foreign materials in banknote paper was that by Benjamin Franklin when he used pieces of crushed mica in an attempt to produce a special paper.
Whilst this particular initiative did not lead to continued success, the use of coloured and fluorescent fibres has been extremely successful. The use of colour fibres was patented by a Mr Wilcox of Philadelphia and first used in banknotes of the United States of America from around 1869. The paper is properly called “Wilcox” paper after its inventor, but is also called “granite” paper because of a similarity of the red and blue fibres to the grain in granite.
The embedded fibres are usually made from natural materials .Wilcox’s original paper had dark blue jute fibres whilst other paper has had silk fibres, such as the Spanish notes at the turn of the century.
Whilst the commonest form of fibre embedded paper is the use of an even distribution of fibres on both sides of the notes, such as the notes of the British Linen Bank, there can be many variations. The one thousand mark Reichsbanknote of 1910 has coloured fibres appearing only on the left-hand side, at the front of the note; whilst the Swedish notes of the 1890’s had either a strip of blue or red fibres at one edge of the note, depending on the denomination.
Depending on the requirements of the note issuing authorities, the paper manufacturers can change the distribution and number of fibres in the paper. This has in fact been done at various intervals by the U.S. Bureau of Engraving and Printing for their various issues in an attempt to confound forgers.
Whilst most embedded fibres are distributed randomly through 9areas of the paper, the 1895 1000 pesata notes of Spain had a strip of woven fibres, similar to a bandage, running between the panel used for cutting from the counterfoil and the main note itself.
Fluorescent fibres are relatively new, dating from the 1960s. These fibres are not visible under normal light, but under ultraviolet light the fibres glow green/white. Most papers that have these fibres have the threads spread quite sparsely on the notes.
Whilst most fluorescent fibres glow green (or green/white), there are some that glow blue and others that glow red. For example the Argentinian Australs have green fibres, the latest issue of Brazil have blue fibres, and the latest one riyal of Qatar has green and blue fibres, whilst the 1984 10,000 pesos of Bolivia has green, blue and red fluorescent fibres.
A natural progression with the use of fluorescent fibres is to combine them with coloured fibres. This has been done with the penultimate issue of the British Linen Bank and the Argentinian Australs, amongst others.
A variation on the embedding of fibres in paper was developed in 1906 when the German company of Giesecke & Devrient took out a patent on the embedding of small printed colour strips in the paper. Examples of paper with these embedded strips can be seen in the 1936 issues of Spain where the strips have “Banco de España” printed on them.
In 1939 Giesecke & Devrient took out another patent for implanting small printed pieces of metal (sometimes called planchettes) in banknote paper. Examples of banknotes printed on this type of paper can be seen in the 1979 issue of Haiti (this series was also the series which was issued in plastic, with both types of notes circulating at the same time).
The final security feature that belongs to the process of paper manufacture is the security thread. The use of security threads is a logical extension of the embedded fibre - a thread of natural or synthetic material placed in the paper during manufacture - except that with the security thread, it is placed regularly in each note.
Whilst most people are familiar with the metallic threads and their successors, there is at least one precursor: the 1871 issue of El Banco de España. This issue carried a “worsted fibre” that was embedded in the notes near the counterfoil and to all intents and purposes appeared much as our modern security threads do.
The modern security thread was developed in the 1930’s as a joint project between Stanley Chamberlain of the Bank of England Printing Works and Messrs Portals Limited, the security paper manufacturer. The result of their collaboration was the metallic security thread that most of us are familiar with, such as was used in the Australian decimal series.
The Bank of England first used their new thread in their £1 and 10 shillings issues of 1940; however it is probable that the very first use of the metallic thread was in the one pound issue of South Africa dated 19.9.1938. Series A78 of this issue was printed on paper with a metallic thread; however because subsequent series were not printed on the same type of paper it can be supposed that this was a trial use in association with Portals and the Bank of England.
The use of threads has grown to become almost universal, as it is almost impossible to reproduce. However, in an effort to confound the would-be forger, several variations on the use of threads have been developed - these being the “Morse code” thread, the “broken” thread, the “microprinted” thread, the “contoured” thread, and the “windowed” thread.
The Morse code thread is a synthetic thread which has sections of the thread being solid and sections being translucent. When held to the light the broken line created by the solid sections can be read as Morse code characters of dots and dashes. The first two issues of Kuwait used such a thread, with the Morse code spelling KUWAIT.
The use of a broken thread can be seen in recent notes from the Phillipines, where threads with regular even breaks are used. The current issue has coloured broken threads, and the previous issue had a black broken thread.
The microprinted thread is also printed on a synthetic thread. This thread is usually translucent, and when held to the light displays a regular pattern on the thread; however when subject to magnification, the “pattern” is seen to be microprinted writing. Usually, the writing is the name or initials of the issuing authority. The Royal Bank of Scotland had the letters “RBS” in past issues, the notes of Qatar have “Qatar Monetary Agency”, and the notes of Banco Central de Bolivia have “Bolivia”.
The contoured thread is a wide thread that has one straight side and one wavy side, with the wavy side pointing either to the left or right on the banknote. This feature appeared in the Bank of England’s fifty pound note that was issued in 1981, as well as in the five hundred kronor note of Sweden that was issued in 1986.
The windowed thread, also called the “Stardust” thread, is the latest development in the use of security threads. These can be seen in the latest issues from England, as well as some of the new issues from Germany, Zambia and Nigeria. When the note containing the windowed thread is viewed from the reverse, the thread looks much the same as a normal thread, although slightly broader. When viewed from the obverse, it looks as if the thread has been woven through the paper. These threads are coated with aluminium, which protects the exposed areas, and gives them their distinctive lustre.
The lustre on the windowed threads is important as it is impossible to photocopy. This distinctive feature has recently been copied by the West African States who have placed a tape on the front of their notes to the left of the security thread. The tape is clear with sections of a shiny metallic surface at reglar intervals, thus inhibiting the photocopying forger.
One interesting variation on the metal thread is that used by Saudi Arabia. Their metal threads are made of silver, because until the issue of banknotes, they had a silver standard and the use of a silver thread is used to reflect the history of that standard. The latest notes from Saudi Arabia also have microprinting on the silver threads, showing that microprinting doesn’t have to be done using only translucent synthetic threads.
The latest development in the field of security threads seems to be the use of security threads that react to ultraviolet light. The notes of Bolivia have threads which glow under ultraviolet light, and the commemorative 60 baht note from Thailand has a microprinted, coloured, broken thread where the blue sections glow when placed under ultraviolet light. Will the variations never end!
Let’s now move on to security features that are developed in the printing process. During the 18th and 19th centuries the printing of books and newspapers were done with printing presses containing moveable type, but maps, bookplates and banknotes were done primarily with copperplate engravings. Although at least one German bank issued notes in 1825 which were printed from stone engravings, and the early Swedish notes and some other European notes did use the letterpress for note production.
Whilst copperlate engraving reached great heights of sophistication, the engraver’s art was not used to its limit in the earliest notes. Not only were the early notes quite plain with the content of the notes being the details of the Bank and its promise to pay, but the quality of work was often substandard and easily forged.
During the middle of the 18th century, banknotes began appearing with vignettes; and the use of delicate vignettes was discovered to be one of the best anti-forgery devices yet introduced.
Nearly all attempts to reproduce vignettes by forgers were failures. Even in the 20th century, the Nazi forgeries of the Bank of England notes failed to reproduce the vignette of Britannia to a high standard.
In the early part of the 19th century, security printing was changed forever with the advent of the steel printing plate. One of the difficulties that the copperplate printers faced was the easy wearing properties of the copper plates. With the subsequent need to copy the plates quite frequently, there was a disincentive to undertake elaborate designs. Steel printing plates removed this difficulty.
With the steel printing plates, the engraving is first done on a soft steel plate which is then hardened - this plate is the die plate. The die plate is then used to make impressions on other soft steel plates which are in their turn hardened and used for printing.
With the introduction of steel plates came the further development of artistic decorations on banknotes. Because only a master die was necessary, much more time and money could be spent in preparing the one die than could ever have been spent in engraving many printing plates.
Banknotes of the late 19th and early 20th century show the use of steel plates at their peak. Allegorical designs were prominent, and there was a great deal of decoration done with “engine” work. Engine work is done with geometric lathes which engrave symmetrical patterns with many lines on to the plates. This type of decoration is often found on the back of banknotes, and is almost impossible for a forger to reproduce.
Another tool, the “stump engraver”, was used to engrave words onto the plate in very small type and often in a pattern. It was not unusual to have the name of the bank, or the denomination of the note printed many hundreds of times on a banknote as a background pattern. The reproduction of “engine” work and engravings by a “stump engraver” were almost impossible— until the introduction of photography.
The invention of offset printing and the advances in intaglio printing have meant that very complex patterns can be used in the production of banknotes. Combining these two methods (as most security printers do) give the banknotes very special properties. Whilst the offset process is used to give the banknote its background, (and often the principal design,) the intaglio print is used to highlight the main points in a design or particular features.
One recent feature to use the offset printing process as a security measure can be found in the new New Zealand five dollar note. The pale green and orange area that contains the watermark looks as if it has been printed with even colouring. However when viewed under magnification, it can be seen that the area is created by many fine coloured lines on a white background. These lines are drawn in a pattern similar to “crazy paving” and when the note is photocopied the lines and patterns become apparent.
This effect occurs because the human eye balances the colours held in the fine lines with the white background; whilst the photocopier makes no allowance for balancing the colours and just copies the lines.
Intaglio printing with its raised lines is almost impossible to be forged in large runs, due to the expensive process of plate preparation. Intaglio printing also has certain properties which include the ability to use magnetic inks, the ability to include latent images in patterns printed with this process, and the ablity to produce microprinting.
The very first banknotes were printed in one colour - black. The only variation on this was a seal which was sometimes stamped on the note by the issuing authority, such as the two red seals on the Ming notes.
The first notes to have more than one colour had distinct features of the note in different colours, but the features were separate. The first British note to have three colours was Royal Bank of Scotland’s one guinea note of 1777—it was printed in black, with the head of King George III appearing in red, and a panel with the denomination printed in blue.
An interesting attempt at multicoloured printing was made by the Royal Prussian State Printing Works in 1856. They attempted to print an underlay of writing where the words were printed in colour and the colours of the letters changed every four or five letters. Unfortunately, because so many notes were spoiled in the attempt to get the printing correct, the process was abandoned.
There was no real incentive to use colours other than black on banknotes until the advent of photography. Around the middle of the 19th century forgeries by photographic means became widely known. To combat this new technology, the security printers reverted to using two colours. In the first instance black ink was still used and the second colour was often red, orange or green - but it was soon discovered that if a note with these colours was photographed using a monochrome plate then the image could still be reproduced, and could be passed as an all black note.
It was during this period, around the 1860s, that the notes of the United States of America moved to the use of green intaglio ink as it was believed that the green ink could not be copied by photography. Unfortunately, technology has moved on but tradition (the Achilles heel for issuing authorities) has dictated that the green ink remains.
Elsewhere it became popular to use blue and red as the two colours, due to the inability of the photographic emulsions of the time to correctly render the two colours (at the opposite ends of the spectrum) onto the negative.
From two colours, the security printers moved quickly to three, with the third colour usually being an underlay - to colour the background of the note. This colour was usually orange or yellow.
Whilst most variations in colour occur with the lithographic (or offset) printing process, the intaglio process is usually left to one colour. Exceptions exist of course, and the 1871 issue of Spain had three colour intaglio printing on a lithographic background, and the Australian bicentennial note issued in 1988 also has multicoloured intaglio printing.
With the development of colour photography the reliance on colours as a major security feature diminished, and colours on banknotes were primarily used to distinguish between denominations.
However the new technology of colour photocopying, and particularly the accessability of these copiers to the general public, has made the security printers rethink their choice of colours. Recent issues from both England and the Netherlands have chosen colours which are difficult to balance on photocopiers. This means that if one colour of a copy is incorrect, any attempt to balance the colour correctly on the photocopier will throw another colour on the copy out of balance, thus making life difficult for the casual counterfeiter.
Magnetic inks have been with us for many years, with their most common use being the numbers printed along the bottom of cheques. Most people will be familiar with the special fonts used to write these numbers. These fonts were required to enable the numbers to be deciphered by the magnetic readers.
Technology has improved over the years, and the need to use specialized fonts has disappeared. Many authorities now use magnetic inks in their serial numbers which can be read by their sorting machines.
Serial numbers are ideal for using specialized inks as they are usually printed on the banknotes as a separate run, and thus specific attention can be given to the inks used.
One use of magnetic inks was in the “CMC7” encoding given to £1 and £5 notes of the Scottish issues from the late sixties to the early eighties. Since no Scottish bank can issue notes of the other banks, they need to exchange their notes after receiving deposits. This is done at the “Note Exchange”, and to expedite the sorting, small patterns of lines in magnetic ink were printed on the back of the notes - these marks were read by the sorting machine and sorted according to bank of issue and denomination.
Whilst it is probable the use of magnetic inks is widespread, it is very difficult to confirm due to the equipment needed for recognising its use. Certainly, the sorting machines used by the U.S Bureau of Engraving and Printing utilise optical and magnetic scanners, indicating that they use magnetic ink. Since 1975 the German Central Bank, and from 1978 the Bank of Spain have used machine readable information for sorting and counting banknotes - it is almost certain that the machine readable codes are in the form of magnetic inks.
Magnetic inks are designed to hold a magnetic field for a short period of time. When a note with magnetic ink is passed through a sorting machine it is subjected to a magnetic field, further into the sorting machine the ink is tested to see if the magnetic field is present - if it is not the note is rejected.
Intentional mistakes were sometimes introduced into the production of a banknote in an effort to detect forgeries. The best documented case of intentional errors is that of the Bank of England white notes which were forged by the Nazis. These errors have come to light because of the desire to publicise the forged notes.
The “white” notes of the Bank of England were issued from 1793 until the mid 1950’s. Despite the dramatic changes in security printing that went on around them, the directors of the Bank persevered with the simple design of the white notes because they were known and accepted throughout the world.
Because of the relatively simple design of the notes, the Bank introduced errors which forgers might assume were simply examples of poor printing. In the case of the five pound note, the letter “f” in the phrase “Comp. of the” had an incomplete lower section, and the word “Five” has flaws in the printing which are the same throughout the issue. The Nazis actually discovered 150 security checks on the different notes which they forged, but they still didn’t get them all.
Another example of an intentional mistake was the use of embossing dies that were purposely cracked. The use of “cracked” dies is known in issues of the German states of Erfurt and Baden.
Ever aware of the possibility of forgers, some note issuing authorities have resorted to placing warnings to forgers on their notes; but it is difficult to determine the effectiveness of these warnings.
The ancient Chinese “Ming” notes carried the following warning: “To counterfeit is death. The informant will receive 250 taels in silver and in addition the entire property of the criminal.” Some French assignats also carried a similar warning: “La loi punit de mort le contrefacteur. La Nation recompense le denonciateur.” This translates as a warning that the law will punish the counterfeiter with death, and that the country will reward anyone who denounces a counterfeiter.
Many European banknotes carried warnings to forgers, and one of the more interesting warnings was one printed in English that appeared on a Prussian banknote. This was included because English counterfeiters had been turning their hand to the the Prussian notes with uncomfortable results for the Prussians.
Although not widespread, the warning to the counterfeiter still exists. The second issue of Katanga in 1962 carried a warning, and the recently superseded West German notes carried a warning which was revamped by some adventurous counterfeiters during the 1980’s - the warning was changed to read: “Whoever counterfeits this note ... will be forbidden to drink for not less than two years.”
The latest release of the Bank of England five pound note introduces a different kind of “warning”. In the bottom margin of the note, on the front and back, international copyright is claimed by “The Governor and Company of the Bank of England 1990”.
This claim to copyright is undoubtedly designed to enable the Bank of England to control the use of the new design, as previous banknote designs were used on tea towels, postcards and other souvenirs. The side effect of this measure for the forger is that they can now be prosecuted for breach of copyright as well as counterfeiting!
Serial numbers were first introduced to ensure that every note was accounted for, and this remains its primary function. The forger may not consider the serial number in itself a sufficient deterrent, but there are several modern variations on serial numbers that do try and hinder the forger.
Many banknotes now print the serial numbers in two colours. The Australian one hundred dollar note has one serial number printed in black and one printed in blue. The current Bolivian notes have one number printed in black and one in red.
Some countries have the two serial numbers printed in different type faces. The current banknotes of Brazil are an example of this, with one type face being angular and the other rounded.
Of course these two features can be combined, and they were combined on Australia’s bicentennial $10 note. Here we have the two serial numbers in different type faces and different colours—blue and maroon.
The new issues from the Bank of England have an interesting development, with the serial numbers being multicoloured. Not only do the colours change on the serial number, but the individual numerals can have more than one colour used to print them.
In some instances there may be separate reasons for handling the serial numbers in a certain way, but a side effect can be the difficulty that the serial number then poses the would-be forger. One example of this is seen in banknotes of Thailand, where the serial number is written once in Thai numerals and once in Roman numerals; and another example is an issue from the Netherlands where the serial number is written as a bar code as well as in Roman numerals.
The new Fijian notes have added a new dimension to the serial number by printing one number in the usual horizontal manner, and one vertically. This method would appear difficult for a forger to imitate, especially if they intended to use different serial numbers on each of their forgeries.
Another recent variation is the “tapered” serial number where the first letter or number is small and the following letters or numbers increase in size. The current issues of Malawi have this feature, and they have complicated the task even more for the forger by having one serial number tapered vertically and one horizontally.
It is interesting to note that there is only one serial number on the new Australian five dollar note, and this may indicate that any security associated with the repetition of the serial number is now becoming obsolete.
Nearly every new issue of the last ten years has an example of perfect registration or counter registration. Perfect registration occurs when a pattern on one side of a note becomes perfectly aligned - or registered - with the pattern on the other side of the note. Counter registration occurs when a pattern on one side of the note complements a pattern on the other side of the note to form a new pattern. Both can be checked by holding the note to the light.
Whilst the use of registration has become very common in recent years it was originally attempted in the 19th century. The first example of registration occurred in an issue of the Vienna State Bank in 1806, and consisted of certain elements on the front of the note being printed in reverse on the back of the note. Thus when the note was held to the light the words “Funf-Hundert Gulden” and various other devices registered perfectly.
Other examples of early registration can be found on the Frankfurter Bank’s 35 gulden issue of 1855 and the two gulden note of the Baden Government issued in 1849.
Modern examples of perfect registration can be seen in the current series of the Royal Bank of Scotland and Saudi Arabian Monetary Agency, although simple perfect registration seems to be giving way to counter registration in most issues.
The new Australian five dollar note has an example of counter registration: to the top right of the Queen’s head is a small circle with a blue pattern in it, on the reverse of the note is a similar circle with a pattern in purple. When the note is held to the light the patterns combine to form the seven pointed Commonwealth star.
The 200 cruzeiros note of Brazil uses counter registration with a pale blue pattern of diamonds on one side, with gaps in the pattern, and a dark blue pattern of diamonds on the other. When the pale blue side is held to the light not only does the dark blue pattern on the rear fill in the gaps but it also appears to be the same shade of pale blue as the diamonds at the front - the colour losing its intensity through the paper.
The ability to perfectly align mass produced modern notes is due to the advances made in printing, whereby the front and back of the notes are printed at the same time, thus ensuring alignment. But despite the efforts of the printers, “perfect” registration is not always perfect - examples of the new Australian five dollar note show that the alignment is not quite perfect as intended.
The use of fluorescent inks is becoming increasingly widespread, with most new issues having some aspect of the note being susceptible to ultraviolet (UV) light. There are three ways that fluorescent inks can behave when subject to UV light; they can change colour, they can glow brighter, or they can “appear from nowhere”. Inks that don’t react to UV light tend to become dull.
An example of changing colour can be seen in the serial number of the new Australian five dollar note. When the serial number is viewed under UV light it turns from purple to green. The same effect can be seen on the signature that appears on the current Omani banknotes - it turns from black to green.
To see a colour glow brighter under UV light we can turn to the 1000 pesos note of Bolivia (P.167). Next to the area of the watermark are a pink and a green line, and whilst these lines appear to have the same colour as other areas of the note under normal light, when subjected to UV light the green line, and the green background colours of the central pattern become brighter whilst the rest of the colours become dull.
The same note can be used to demonstrate the ink that “appears from nowhere”. When the note is viewed under UV light the number “1000” appears in bold gold type, yet this disappears when removed from the UV light. The use of inks which react only to UV light is surprisingly widespread, and unless you have a UV lamp you’ll never notice them.
Examples of the use of UV images can be seen on the notes of Oman (Sultan’s image, national symbol and note denomination), Qatar (note denomination), Bahrain (note denomination), Saudi Arabia (King’s image), and the new issues of all Scottish banks have ultraviolet sensitive sorting marks.
UV lights are available in two wavelengths, and these produce different effects on notes with UV sensitive inks. An excellent example of the differences can be seen in the new Australian five dollar note. When the longer wavelength is used the serial number changes to a pale green, but when the shorter wavelength is used the serial number glows bright green. Under the shorter wavelength an additional device of a blue checkerboard pattern also appears at the centre left on the back of the note. (This device is not so apparent under the longer wavelength.)
An interesting variation of UV ink was mentioned in an article in the Banknote Reporter (October 1985) by Jos Eijsermans, whereby fluorescent ink appears on a 500 Kronor note introduced by Sweden in the mid-eighties. When this note is subjected to UV light, an overprint of a 17th century Swedish note appears; however not all the details of the overprinted note are apparent under UV light. It seems that another sort of light or heat source is needed to make these details apparent.
The use of fluorescent devices means that bank tellers can quickly check suspicious notes, and the sorting machines that many central banks use, will reject any note without the fluorescent device.
A latent image is one which is to all intents and purposes concealed, but under certain circumstances becomes apparent. The current series of the Clydesdale Bank (Scotland) illustrates the use of latent images. On each note there is a pattern of four discs with the denomination illustrated on the left hand disc; however if the note is viewed from a very low angle, the denomination of the note can also be seen in the centre of the discs.
This type of latent image also appears on the current series of Saudi Arabia, where the denomination of the note appears in Arabic numerals in the panel above the King’s portrait. Another type of latent device exists on these notes - there are two fine white lines that appear to the left of the King’s portrait when the note is viewed from a low angle, but seem to disappear when the note is viewed from face on.
Another example of a latent image can be seen on the reverse of the Nederlandsche Bank 250 guilders note. Here there is a small olive green bush - part of the landscape - and if a red filter is placed over this bush a rabbit can be seen within a dark hole. With a good light and viewed at the right angle the image of the rabbit can just be distinguished without the filter.
These latent images always appear in the intaglio printing on the notes, and it is always worth checking the intaglio printing on new issues to try and identify this type of device.
Microprinting has been previously mentioned in reference to security threads, but it is now increasingly used on the note itself. To the naked eye microprinting looks like a line on the note, but when magnified can be clearly read. Most attempts to photocopy or photograph the note will not succeed in copying the microprinting with the necessary clarity - although often it is still legible.
Microprinting is always done with intaglio printing and in most cases appears as a line or group of lines. Examples of microprinting can be found on the new Australian five dollar note, the recent issue of Sri Lanka, and the most recent issues of Oman and Saudi Arabia - not surprisingly the microtext in the last two is printed in Arabic. Indeed, new issues without the use of this device would be the exception rather than the rule.
As with all good security devices, it is just a matter of time before variations occur, and the first variation of microprinting is already with us. Whilst microprinting usually appears with the words printed in intaglio ink, examples are now appearing where the background is the intaglio ink and the microprinting is the absence of ink; i.e. the microprinting appears in “reverse image”.
An example of both methods of microprinting can be seen on the new five dollar note from New Zealand. Regular examples of microprinting can be found to the bottom left of the portrait of Sir Edmund Hilary, as well as between the two patterned bars trailing to the right of the portrait. The lower of these trailing bars has an intricate pattern of lines on an intaglio background, and closer scrutiny of this bar will show that letters “NZ” are microprinted many hundreds of times in reverse image.
With the battle against forgers still raging, there are a number of new security features that are just appearing on the scene. Here are a couple of the most notable.
The Optically Variable Device (OVD) that has appeared on Australia’s bicentennial note and Singapore’s fifty dollar note is the brainchild of the CSIRO and Note Printing Australia. The aluminium foil is incredibly thin and is embedded between the strata of the plastic note. The reflecting properties of the OVD are impossible to copy by any current technique - it remains to be seen if they can be forged.
Of course hand in hand with the development of the new plastic note technology, has come the use of the “transparent” area that has been used on all notes - either surrounding the OVD, or with a printed design.
The 100 and 500 rial notes of Saudi Arabia have a metal panel with an “integrated double image”. When viewing the note from one angle, the Saudi emblem of two swords and a palm tree can be seen in the panel; when viewed from another angle the name of H.M. King Fahd Ibn Abdulaziz appears in Arabic. This device is an innovative variation on the use of latent images, placed in a specialised ink.
The 60 baht commemorative note of Thailand has a device in green ink printed on the top left of the note. When the note is viewed at a low angle the colour of the ink turns to a deep blue. It is likely that the use of light sensitive inks, as is used for this device, will become more common.
Whilst we have money we will have forgers. It is in the interests of all the community and especially the note issuing authorities that the integrity of the currency they produce is not damaged by the efforts of counterfeiters.
To this end, most new issues throughout the world are accompanied by an “awareness” campaign, showing pictures of the new issue and highlighting the relevant security features used in the issue. A recent initiative appears on the latest issue from the Netherlands where there are instructions on the note itself to let the public know the three security features they should check for: the security thread, the watermark, and perfect registration.
Collectors should be aware that there are three levels of security features on most notes: those which the public are made aware of, those which institutions such as banks are made aware of, and finally those of which only the note issuing authority area aware.
It is interesting to observe that in the official folder of the Australian bicentennial ten dollar note, the following statement is made: “The watermark, usual in paper notes, has given way to the OVD.” This seems to suggest that there is no watermark or similar feature.
However the handbill distributed through the banks clearly identifies the “Wave pattern (visible when note is held to the light).” This wave pattern is very much like a watermark and the statement on the folder is either intentionally misleading, or just an example of poor dissemination of information regarding the security features.
Whether or not the public was supposed to know in this specific instance, there are certainly many instances where security devices are not publicised. The most obvious is the printing done with ultraviolet sensitive inks.
It is one of the many joys of banknote collecting to try and identify the many and varied security features of each new issue. I trust that this article has helped collectors add a new dimension to their collecting.
In writing this article I have made use of material that has been published in the IBNS Journal, various editions of The Bank Note Reporter, as well as the following books:
This article was completed in August 1993
© Peter Symes