hallmark

On precious metals, a stamped mark that guarantees the quality of the metal and identifies the region of manufacture and, usually, the date and the name of the maker.

Books

Bradbury's Book of Hallmarks: A Guide to Marks of Origin on English, Scottish and Irish Silver, Gold and Platinum and on Foreign Imported Silver and Gold Plate 1544 to 2010

Jackson's Hallmarks: English, Scottish, Irish Silver and Gold Marks from 1300 to the Present Day