What is hallmark? How to use in English

The word "hallmark" originated in the medieval city of York, England, where gold and silver items were assayed, or tested, for their purity. The Assay Office in York was established in the late 14th century, and the mark used to certify the quality of the metal was a leopard's head in a rectangular frame. This mark became known as the "Yorkshire Hallmark" or simply "hallmark." The term "hallmark" is a combination of "hall" which comes from the Old English "hale" meaning "steel" or "hard metal," and "mearc" from "merc" which means "boundary" or "mark." When marking items, instead of stamping a word or name onto the metal, the craftsmen would use three symbols in addition to the leopard's head. The first symbol indicated the purity of the metal, the second identified the maker, and the third symbol showed that the item was tested at the official assay office. Over time, the hallmark became a sign of quality and reliability for buyers, and soon, other cities in England started establishing their own assay offices and hallmarking schemes. Today, the Hallmarking Act of 1973 requires that all gold, silver, platinum, and palladium items sold in the UK above a certain weight are hallmarked at one of four official assay offices in Sheffield, London, Birmingham, and Edinburgh.