The value of jewelry depends on a number of things, including who made the jewelry, the type of metal the jewelry is made from and the date of the jewelry. The law concerning jewelry trademark varies from country to country and has changed within countries over time. Certain principals will help you identify jewelry stamps and trademarks to determine the value of your jewelry.
Examine the jewelry to locate any and all type of stamps. Use a jeweler's loupe that magnifies at least ten times to examine the detail of all found marks.
Check the mark(s) from different directions to be sure your are not viewing it upside-down.
Determine the number of stamps on the jewelry. There are four types of stamps to look for on jewelry: (1) purity mark; (2) maker's mark; (3) dateletter; and (4) town mark.
Evaluate the purity mark. Jewelry marked in a country that has a legally mandated hallmarking system usually has both a purity mark and a maker's mark. The purity mark indicates the purity of the gold or silver. Most countries today (including the United States) require a purity mark for gold and silver.
Evaluate the maker's mark because it indicates who made the jewelry. The makers' mark is the equivalent of a signature. The law in some European countries dictates that jewelry makers include both purity and makers' marks on all gold and silver jewelry. The United States does not require or regulate the signatures or marks stamped on jewelry, whether fine or custom, apart from the typical trademark protections offered by U.S. intellectual property laws.
Check to see if the jewelry has a dateletter. The presence of a dateletter can help narrow down both the date the item was made and where it was made. Jewelry produced in England after 1478 was stamped with a dateletter, indicating the date the gold or silver jewelry was assayed by the government at the Goldsmith's Hall in London. Dateletters are rarely found on delicate jewelry produced in England if there is no room for a full set of marks.
Check to see if the jewelry has a town mark. Jewelry assayed in countries with more than one office included a town mark to indicate the office of assay. For example, the assay mark of Birmingham, England (currently the largest assay office in the world) is an anchor.
Compare the marks to those of known makers. To narrow down your search, seek out a book or website that concentrates on similar jewelry. For example, if you are examining the origins of a sterling silver pin, seek out a source that looks at sterling silver jewelry from the same country and time period based on the clues you found looking at the stamps on your jewelry.