Jewellery hallmarks are words, letters or symbols stamped directly into the metal. These markings can tell you important information about your jewellery, such as what metal it is made of, who made it and even how old it is. If it has a hallmark by a famous maker, your jewellery could also be more valuable, even if it is only costume jewellery. Learning to read the marks can also help you avoid buying fakes or substandard jewellery.
Learn to recognise English hallmarks for gold, silver and platinum. The British symbol for sterling silver is a walking lion. A crown represents gold, along with a number followed by "c" or "ct," for carat weight on jewellery made from the 1700s to 1975. After that, just numbers represented gold purity: 375 for 9ct, 585 for 14ct, 750 for 18ct and 950 for 22ct. Numbers representing platinum are: 850, 900, 950 and 999. Date marks are a letter in a shield and can be decoded with a hallmark guide. Hallmark guides are available in book form or online.
Study hallmark guides to determine European hallmarks for precious metals. Every country has its own set of marks denoting the origin and the purity of metal. Most use a numbered system for gold, similar to the British modern system, but some are more cryptic and need a guide to decode them. Silver marks vary greatly; platinum is usually marked with a number and "PT."
Learn how to read American hallmarks. American precious metals are straightforward in terms of markings. The letter "k," after a number, denotes the carat purity of gold, "sterling" or "925" signifies sterling silver, and "PT" or "plat" is for platinum. The names or initials of the maker will also sometimes appear in the marks.
Familiarise yourself with terms for gold plating. Gold-filled jewellery is marked several ways: filled, GF, 12k or 1/20. Other terms for gold plating are Vermeil (gold over sterling silver), GP (gold plate on base metal), RGP or rolled gold (seen mostly on antique jewellery, a heavier plating than gold filled) and GEP (gold electroplate, the lightest of all the gold plating techniques).
Use a jeweller's loupe to read very small marks on jewellery. Question the authenticity of cheap jewellery with designer names. Even if it seems to have the right hallmarks, it is not always what it seems. Ask to see receipts from an authorised dealer or ask for copies of the original purchase to authenticate used items. Checking the mark against a hallmark guide can also help.
Beware of fake precious metal marks on jewellery from China. Poor plating techniques leave a bubbly surface, and details on the item will look thick, instead of having crisp, fine edges. If you suspect that you have a fake, take your items to a jeweller. The jeweller will have the right equipment to test for precious metal content.