A hallmark is an official mark or series of marks struck on items made of metal, mostly to certify the content of noble metals—such as platinum, gold, silver and in some nations, palladium. In a more general sense, the term hallmark can also be used to refer to any distinguishing characteristic.
Many nations require, as a prerequisite to official hallmarking, that the maker or sponsor itself marks upon the item a responsibility mark and a claim of fineness. Responsibility marks are also required in the US if metal fineness is claimed, even though there is no official hallmarking scheme there. Nevertheless, in nations with an official hallmarking scheme, the hallmark is only applied after the item has been assayed to determine that its purity conforms not only to the standards set down by the law but also with the maker's claims as to metal content.
In some nations, such as the UK, the hallmark is made up of several elements, including: a mark denoting the type of metal, the maker/sponsor's mark and the year of the marking. In England, the year of marking commences on 19 May, the feast day of Saint Dunstan, patron saint of gold- and silversmiths. In other nations, such as Poland, the hallmark is a single mark indicating metal and fineness, augmented by a responsibility mark (known as a sponsor's mark in the UK). Within a group of nations that are signatories to an international convention known as the Vienna Convention on the Control of the Fineness and the Hallmarking of Precious Metal Objects, additional, optional yet official, marks may also be struck by the assay office. These can ease import obligations among and between the signatory states. Signatory countries each have a single representative hallmark, which would be struck next to the Convention mark that represents the metal and fineness.
From the Late Middle Ages, hallmarking was administered by local governments through authorized assayers. These assayers examined precious metal objects, under the auspices of the state, before the object could be offered for public sale. By the age of the Craft Guilds, the authorized examiner's mark was the "master's mark", which consisted frequently of his initials and/or the coat of arms of the goldsmith or silversmith. At one time, there was no distinction between silversmiths and goldsmiths, who were all referred to as orfevres, the French word for goldsmith. The Master Craftsman was responsible for the quality of the work that left his atelier or workshop, regardless of who made the item. Hence the responsibility mark is still known today in French as le poincon de maitre literally "the maker's punch". In this period, fineness was more or less standardized in the major European nations (writ: France and England) at 20 karats for gold and 12 to 13 lots (75% to 81%) for silver, but the standards could only be partly enforced, owing to the lack of precise analytical tools and techniques.
In 1300 King Edward I of England enacted a statute requiring that all silver articles must meet the sterling silver standard (92.5% pure silver) and must be assayed in this regard by 'guardians of the craft' who would then mark the item with a leopard's head. In 1327 King Edward III of England granted a charter to the Worshipful Company of Goldsmiths (more commonly known as the Goldsmiths' Company), marking the beginning of the Company's formal existence. This entity was headquartered in London at Goldsmiths' Hall, from whence the English term "hallmark" is derived. (In the UK the use of the term "hallmark" was first recorded in this sense in 1721 and in the more general sense as a "mark of quality" in 1864.)
Complete international hallmarking has been plagued by difficulties, because even amongst countries which have implemented hallmarking, standards and enforcement vary considerably, making it difficult for one country to accept another's hallmarking as equivalent to its own. While some countries permit a variance from the marked fineness of up to 10 parts per thousand, others do not permit any variance (known as negative tolerance) at all. Many nations abide by the Vienna system and procedures are in place to allow additional nations to join the Vienna Convention. Similarly, with the consent of all the current member states, the terms of the convention may be amended.
The Hallmarking Act 1973 made Britain a member of the Vienna Convention as well as introducing marking for platinum, a recognised metal under the Convention. All four remaining assay offices finally adopted the same date letter sequences. In 1999 changes were made to the UK hallmarking system to bring the system closer into line with the European Union (EU). Note: that under this latest enactment, the date letter is no longer a compulsory part of the hallmark.
The Netherlands, who are members of the International hallmarking Convention, have been striking hallmarks since at least 1814. Like many other nations, the Netherlands require the registration and use of Responsibility Marks, however, perhaps somewhat unusual, there is a book published entitled "Netherlands' Responsibility Marks since 1797" (in three volumes and in the English language) illustrating all the responsibility marks registered there since that time. This is significant since producers that exported precious metal goods to the Netherlands would have been required to register their marks.
Traditionally, the hallmarks are "struck" using steel punches. Punches are made in different sizes, suitable for tiny pieces of jewelry to large silver platters. Punches are made in straight shank or ring shank, the latter used to mark rings. The problem with traditional punching is that the process of punching displaces metal, causing some distortion of the article being marked. This means that re-finishing of the article is required after hallmarking. For this reason, and that off-cuts from sprues are often used for assay, many articles are sent unfinished to the assay office for assay and hallmarking.