Hallmark embossed on silver plate.
A quest for Authenticity – Maria Luisa Vitobelo, Thilo Rehren
Hallmarks, which are special marks stamped onto precious metal articles, provide different information about these products (where and when they were made, who made them). In particular, they guarantee the declared fineness of the used material; for brevity, the following text uses several times the term "hallmark" including maker's mark or responsibility mark as welL which are explained later on. Even in today's era of precision manufacturing, every new hallmarking die is unique; it is impossible to make an exact reproduction. The production of hallmarking dies is a highly professional activity requiring, on purpose, a good portion of manual work. Traces left by engraving tools are the reason why we can find many unique characteristics even on the minute area of the hallmark embossment. When the surface is magnified, we can see these distinctions and identify the differences of seemingly identical hallmarks (in this page, first photo from the top). This was and still is the way to discover forged, illegal hallmarks.
Legal hallmarks were often registered and samples kept in different places as reference marks, imprinted e.g. on copper plates (in this page, second photo from the top). In case of any doubt, it was possible to compare a suspicious hallmark with these samples and to discover a fake. Hallmarking of precious m~tals is an extremely effective weapon against fineness fraud. The system of hallmarks also makes the uncontrolled circulation of strategic materials, which precious metals have always been, more difficult.
Why are hallmarks forged? A fake hallmark makes it easier to sell poor quality products, the fineness of which is lower than that declared on the hallmark. A fake hallmark can also be used even when an article has the right fineness, because a false hallmark confirming an official inspection helps avoiding fees or custom duties. Unauthorized use of a maker's quality mark is a similar case: we can often see a fake maker's mark on imitations of successful products.
Counterfeits have always relied on the fact that it is practically impossible to tell the fineness of a metal from which an article is made without use of special devices. This is why different institutions and prominent individuals (rulers, goldsmiths' guilds, rich merchants) needed to have some way of making sure that besides a great look - which, in the case of fakes, often does not actually last - an artefact also has the declared value. This had been done for millennia with coins, stamped by the official mint. A similar system has gradually developed for jewels and other articles made of highly valued metals (initially gold and silver and, much later, also platinum and palladium): articles made of guaranteed precious metals were stamped with a small, but complicated and hard-to-imitate mark.
Hallmarks started being widely used after the first goldsmiths' guilds were founded in the 13th century. As tim·e went by, every goldsmith has created his own mark, usually with his initials that were engraved in differently shaped frames to distinguish them (next page, first photo from the top). Some records of these early hallmarks still exist and thus, even after many centuries, we can often identify the author of a specific article from the hallmark. The guilds were very particular about their reputation and made sure that the products made by all their members were of good quality in every aspect, and usually guild members themselves inspected these products. The objective was to guarantee the quality of the work as well as th'e metal for its customers. This guarantee was especially important for products exported to other regions. Maker's marks and hallmarks of a goldsmith or guild not only guarantee.d fineness and good quality work, but also provided information about where the articles were made, which helped to promote the good reputation of their makers.
Several factors helped to create an environment that radically limited illegal practices. A new goldsmith could not become a member of the guild unless he had many years of experience as a journeyman, passed difficult tests and was vouched for by one of the current guild members with a good reputation. It was not possible to work as an independent goldsmith without being a member of the guild. There were several levels of punishment for those who failed to honour guild regulations, the worst punishment being expulsion from the guild. Guilds were very protective of their territory, and whenever foreign products were sold in their territory, they tried to find any potential discrepancy and thus to limit competition.
Prior to the industrial revolution, it was difficult to abuse hallmarks on a large scale thanks to the implemented practices. With the on'set of a new era, the situation has changed: cheap batch production and an easy circulation of goods affected the goldsmith trade as well. The traditional structure of guilds and business relations kept changing and the tried and tested guarantees were no longer sufficient - there was more room now for fraud.
It was necessary to stop these bad effects in the dynamic and chaotic atmosphere of the industrial revolution, and it was in the state's best interest to implement effective inspections of goldsmith products. Therefore, most European countries established specialized offices - assay or guild institutions - and provided them with the necessary regulatory authority. Since the time of their foundation, their task has been practically the same: to test the fineness of all precious metal articles, to inspect fineness marks and maker's marks that are mostly imprinted by the actual makers, and to imprint hallmarks proving the inspection. Strictly speaking, the term "hallmark" means only the mark imprinted by an inspection institution independent from the maker (in this page, second photo from the top).
The separate fineness marks and maker's marks are also stamped onto precious metal articles and are often included in the term, although they do not carry the same official authority. Today, most countries have a sophisticated system of marks from which we can easily find out the necessary information about the metal and its fineness, the maker and the place- of inspection. The assay offices keep records of all these marks.
Assay offices often have the right to perform random on-site inspections to check whether the products that are being sold have been properly inspected and do not carry false hallmarks or incorrect marks. The inspection systems in many countries are similar but not uniform.
Assay offices seek modern devices that would help them to discover any discrepancy. Touchstone testing that provides good basic information is the simplest and oldest method. Fire assay by cupellation, i.e. the separation of precious metals from other metals by oxidizing fusion, is a very accurate method of checking the contents of precious metals in an alloy. This method, known since medieval times, allows us to determine fineness with the accuracy of up ~o two ten-thousandth.
Modern non-destructive methods of analysing precious metal alloys include, besides others, elemental analysis by an electron beam with energy-dispersive analysis, EDA, or the more commonly used X-ray ftuorescence analysis (XRF). High quality optical or electron microscopes are used to check hallmarks, and are indispensable for conclusive identification in court.
Thanks to the cooperation of assay offices in different countries, the best offices share their experience with other offices. The Assay Office in Prague, founded in 1806 as c.k. Affiliated Assay Office Prague, is also involved in such cooperation. The following experiments were carried out in cooperation with its laboratory.
We hardly ever see a totally clean and undamaged surface when examining hallmarks and other marks on old precious metal articles. The purpose of these experiments was to find out whether or not it is possible to find unique characteristics on damaged (partially worn) hallmarks.
The experimental samples consisted of silver metal plate strips with six different hallmarks imprinted on them.
The strips were then subjected to four different ways of degradation of a different degree (wear, repair by fire, corrosion and mechanical cleaning of an article); the goal was to find the ideal way of looking for unique characteristics that survive such treatment, and to determine the limit where the identification of unique characteristics is no longer possible or possible only with great difficulty.
The surface of the samples imitating regular wear was sanded and polished to a different degree. Hallmarks are usually stamped deep enough and therefore even significant wear does not change the hallmark embossment. Yet, there are cases where e.g. wearing a ring for a long time may cause such loss of the metal that dam,ages the hallmark embossment. The sample imitating this situation proved that it was still possible to identify the unique characteristics of the hallmark in the bottom part of the embossment.
The next sample imitated a repair of the jewel by fire: the metal was annealed to the temperature that causes oxidation of the surface due to the presence of copper in the alloy. When the oxidized layer was chemically removed it was obvious that the imprinted hallmark had lost its most delicate characteristics but was still in a state good enough for examination of the embossment. Subsequently, a thick layer of patina on the sample imitating an archaeological find was artificially created. By its chemical removal, a situation was imitated where the surface of a jewel is usually damaged even if corrosion is removed very carefully. In this case, the entire surface, including recesses, of the hallmark was damaged. Identification was difficult. In such cases the size and especially the characteristics of the damage must be assessed. Damage by corrosion is easy to recognize.
However, few archaeological finds of artefacts that would today require hallmarks are from periods when hallmarks were used, and the difficulty to make a fake archaeological find with a fake hallmark looking real minimizes the risk of circulation of such imitations.
On the samples imitating mechanical cleaning, the effects of cleaning with fine abrasives using fine nylon, brass or glass brushes with a different level of intensity were examined. After having applied regular force necessary to clean the surface, one could still see enough areas, especially in the recesses of the embossment, to identify the hallmark.
After all these tests representing regular degradation, repair and cleaning, it was still possible to see the identification characteristics of hallmarks in the electron microscope. In reality of course, identification is much more complicated due to the large number of marks that have been used, where especially the old ones are often not registered. Nevertheless, the tests have shown that the traditional way of hallmarking still provides efficient protection against the different types of fraud mentioned above. Thus, there are good reasons for creating a comprehensive database of currently known hallmarks so that newly examined hallmarks could be easily and quickly compared.
The samples artificially damaged in such an extreme way making identification impossible show signs of obvious tampering. If someone wanted to disguise forged hallmarks this way, such extreme damage of the embossment can be discovered by a regular optical microscope. If we see similar damage in real life, we can most likely assume that the damage was done on purpose to make identification impossible.
Another way of forging hallmarks is taking a mould of the entire original, including its hallmarks, and reproducing it using lost-wax casting, which makes accurate reproductions. The fact that a hallmark must be metal stamped and not cast is crucial for distinguishing the original from the reproduction. The surface of a casting is completely different from that made by the hallmarking die and, when magnified, it is easy to see the difference. This is demonstrated by another experiment com'paring the surface of a stamped hallmark with that of a casting.
It is also possible to deceive customers by moving a legal hallmark to another jewel. The traces of soldering can be carefully effaced and, in such a case, it is difficult to discover a fake. The goal of this rather rare type of forgery is to make an imitation of an especially valuable artefact look real.
The fight between counterfeits and inspection continues and has become more and more sophisticated on the part of both sides. Counterfeiting is becoming more frequent and precise, and is being discovered by more and more sophisticated techniques. Cutting-edge devices are used to discover imitations, and it is often necessary to cooperate at an interdisciplinary level in order to assess them. A stamped hallmark will remain a good identifying characteristic in the future, although counterfeits will undoubtedly continue imitating them. The goal of the experiments made as part of the AUTHENTICO Project was not only to help to improve the method of detection but also to find simple methods of initial inspection that could be widely applied.
ILLUSTRATIONS AND ACKNOWLEDGMENTS:
SEM views Assay Office Praha.
Pp. 86, 87
Photos by Andrej Sumbera.
The author wishes to thank and acknowledge Ing. Martin Novotny. Director. Praha Assay Office. for his learned contribution and for granting availability of facilities and SEM equipment.