Where necessary our jewellery will carry a London hallmark where my sponsors mark has been registered since 1981.
A Hallmark is a guarantee of purity or fineness in precious metals. What is now recognised as a modern hallmark began in the year 1300 when Edward the 1st attempted to regulate the purity of craftsmen's items. An external group called "The Guardians of the Craft" were a group who went from shop to shop to assay the metals used by craftsmen and strike the "Leopard's Head" mark where necessary.
In modern times, hallmarking (where required due to weight) is done by an assay office. There are 4 assay offices in the UK,London,Birmingham, Sheffield or Edinburgh. The metals are tested for purity and fineness and then the correct mark is struck. The mark can be punched onto the metal with a small metal stamp or can now be applied by a laser.
"no goldsmith... shall from henceforth make or cause to be made any manner of vessel, jewel or any other thing of gold or silver except it be of the true alloy... and that no manner of vessel of silver depart out of the hands of the workers, until further, that it be marked with the leopard's head".
Excerpt from the statute of Edward 1 in 1300
My jewellery (where necessary) carries my sponsor's mark, a standard or fineness mark for the metal used, eg sterling silver or gold (9,18 or 22ct), the assay office mark and a date letter mark.