Identifying and authenticating antique and period jewelry is based on experience and knowledge. It is often a process of comparing known with unknown and making an educated guess. But those of us who search for clues to a piece's age and origin are always delighted to find a hallmark on a jewel, because it eliminates a great deal of guesswork. Learning how to identify hallmarks is an essential part of becoming an expert in the field.
There is a common misunderstanding about what a hallmark really is. Many people confuse hallmarks with makers' marks. A hallmark is nothing more than an indication of metal content, a guarantee of purity or quality, which may include a maker’s mark and other marks. Makers' marks alone are not considered hallmarks. Hallmarks are most often found on precious metal objects. Jewelry is exempted from hallmarking under certain circumstances. However, when a piece of jewelry is hallmarked, the marks can yield clues to country of origin and, sometimes, date of manufacture, as well as indicate the metal content of the piece.
The word hallmark is derived from London's Goldsmiths' Hall of the Worshipful Company of Goldsmiths, the originator of Britain's first hallmarks, which still maintains a record of all British hallmarks. The most accurate definition of a hallmark is the mark or marks stamped, impressed, or struck on gold, silver, or platinum which indicate fineness or karat (also called quality or purity marks). Depending on country of origin, hallmarks can also include symbols for place of assay, date of assay (in the form of a letter or a letter and a number), maker’s mark, importation or exportation mark if applicable, and tax or duty mark.
Hallmarks have been in use in England and France since the 14th century. Most other European countries also use hallmarks. The United States has never used hallmarks per se. Indications of fineness or karat have been required since 1906, but fineness marks were sometimes stamped on silver jewelry in the 19th century (“coin” or “standard” for 900 silver, "sterling" for 925).