There are four precious metals which require hallmarking, namely silver, gold, and more recently platinum and palladium.  Put simply, hallmarking is a legal requirement in the UK to enable an item to be described and sold as silver if it contains 7.78g or more of silver or gold if it contains 1g or more of gold. Compulsory hallmarking means that you will always have a guarantee of quality as each item is tested for purity at the Assay Office before hallmarking.

The only exceptions to this are precious metal items which weigh under the relevant specified weights and although they can still be hallmarked, they are often just stamped 925 for sterling silver or 999 for fine silver. 

There are only four Assay offices in the UK, located in London, Birmingham, Sheffield and Edinburgh. The London Assay office, being the oldest, was set up in the 1300s in Goldsmith’s Hall in the City of London where craftsmen were first required to bring their silver and gold goods to the Hall for assaying (testing) and marking with the leopard’s head.  This was said to be taken from the royal arms of King Edward 1 and later known as the King’s mark. Platinum and Palladium are now also required to be hallmarked since 1975 and 2010 respectively.

My maker’s mark is registered at the London Assay office and all of my hallmarked jewellery is sent to Goldsmith’s Hall for assaying and marking with the traditional 5 marks: maker’s mark, millesimal fineness mark, the traditional fineness symbol, the historic leopard’s head and date letter representing the year the item was made.

For more information please go to https://www.assayofficelondon.co.uk/hallmarking/what-is-a-hallmark