What Are the Tiny Stamps on Silver? A System for Catching Fraud

Silver and gold are valued by their purity, and pure metal is too soft for most objects, so they are alloyed with copper or other metals, which lowers the value and cannot be detected by looking. A buyer therefore has no way of verifying what they are paying for, and a maker has every incentive to add more base metal than declared. The response, developed in several European jurisdictions from the medieval period, was compulsory independent testing before sale, carried out by an authority separate from the maker, with the results punched into the object as a permanent record. That arrangement is one of the oldest forms of consumer protection in existence and it predates almost every other kind of product standard.

A full set of British marks carries several distinct pieces of information:

• •The maker's mark, identifying who submitted the item, usually initials in a shaped surround
• •The standard mark, indicating the purity attained, with different symbols for different standards
• •The assay office mark, identifying which office tested it, each having its own symbol
• •The date letter, a letter in a particular typeface and surround indicating the year
• •Duty marks in periods when tax was levied, showing it had been paid
• •Commemorative marks applied voluntarily in particular years

The procedure that produced the marks was genuinely analytical and the traditional method is worth describing. A small scraping was taken from the object, which is why the process is destructive in a minor way, and the silver was separated by cupellation, in which the sample is heated in a porous vessel with lead so that the base metals oxidise and are absorbed while the precious metal remains as a bead, which is then weighed. Comparing that weight with the original gives the purity directly. The method is very old, appearing in ancient metallurgy, and remained standard for centuries. Modern offices use spectroscopic methods that determine composition without destroying material, alongside the older technique for reference work.

Compulsory marking of quality by an independent authority spread well beyond precious metal. Guild marks on woven cloth recorded that a piece had been inspected for width, length and quality, with seals attached at the finishing stage, and such marks were required across the medieval European textile trade. Marks on pewter, on glass and on ceramics identified makers and in some places quality. Proof marks on firearms record that a weapon was test fired at above normal pressure, and the practice continues under statute in several countries. Gun barrel, silver and textile marking share a structure, in that a buyer cannot verify a property that matters greatly, so an independent authority verifies it once and records the result permanently on the object.

The system produces a side effect that collectors and historians rely on heavily. Because the date letter cycles through an alphabet in a known sequence with a changing typeface and surround, a piece can be dated to the exact year, which is a precision almost nothing else in decorative arts allows. The office mark gives the city. The maker's mark can be matched against registers to identify the workshop, and those registers survive for several centuries in some jurisdictions. That combination means a piece of silver frequently carries more reliable documentation than the objects around it, which makes silver an unusually good source for studying trade, fashion and workshop organisation. It also means fakes are detected by examining the marks, and forging them is a serious offence in its own right.

Purity cannot be judged by eye, so independent testing before sale with results punched permanently into the object is among the oldest forms of consumer protection. Maker, standard, testing office and year are recorded separately. The date letter cycles through a known alphabet with changing typefaces, which dates a piece to the exact year and makes silver unusually well documented.