Hallmarks have been used in England and France as indicators of the purity or quality of precious metal items since the 14th century, and most other European countries use hallmarks as well. Gold hallmarks guarantee the gold content of jewelry, and the hallmark on your antique jewelry item can also can give an authentication expert clues about the country of its origin and date of manufacture. Online or print resources may be used to identify the many specific hallmarks, but to begin with it is important to understand where the marks come from, what they mean and what they include.
National law in most countries requires gold jewelry to be marked with its karatage or fineness. In other countries, the law requires that all jewelry is tested (assayed) by an independent third party, usually an accredited Assay Office, which in most cases guarantees its mark by law. The marks made by the Assay Office, including the karatage or fineness, the maker's mark and the Assay Office mark are known as a hallmark, according to the World Gold Council website.
Indication of Gold Content
Countries may mark with either the gold karatage (or caratage) or its fineness. Karatage is an indication of gold content (e.g., 18K), while “fineness” is an expression of gold content in parts per thousand (e.g., 750, which is 75 percent or 18K gold).
The term “hallmark” comes from London's Goldsmith's Hall of the Worshipful Community of Goldsmiths, the originator of Britain's hallmarks. Earlier than this, the English introduced a basic marking system into law late in the 13th century. The original hallmarks only represented the purity of the metal, with other types of marks being added as the system developed.
Some Common Hallmarks
British hallmarks include a fineness or purity mark, an assay office mark, a date letter, and usually a maker's mark, with the sequence of marks arbitrary. From 1798 to 1975, a crown plus the karat (abbreviated "c" or "ct" for "carat") was used for the fineness or purity mark on gold. In Scotland, a thistle was used instead of a crown. Only gold assayed at 18 and 22 ct was legal and hallmarked from 1798 to 1854. From 1854 to 1932, fineness in thousandths was added. The French have a complex system of hallmarks that uses symbols in the form of animals, animal heads, people, insects and birds rather than numbers. However, the French hallmark that you are likeliest to see is also the easiest to recognize. This is the eagle's head, which has been use since 1838 and indicates 18 karat gold, according to the Modern Silver Magazine website.
A complex aspect of the British hallmark system is the use of date letters for cycles of hallmarks by each place of assay. The date letters begin with A and continue to Z, sometimes omitting J, and sometimes ending before Z, with the style of letter and shape of the reserve or shield background different with each cycle. The date letters can be interpreted using a pocket-sized edition British hallmark book. Simply determine the place of assay and look up the date letter in the tables for the city, explains Modern Silver.