The Goldsmiths' Company Assay Office
The Goldsmiths’ Company Assay Office in London is the oldest assay office in Britain. It has offered hallmarking services since the Worshipful Company of Goldsmiths began in the 14th century. The office received a royal charter in 1327 and is fifth in precedence among London’s 12 great livery companies.
Hallmarking started in the 14th century when Edward I required silver sold in England to meet a standard. The four wardens of the Goldsmiths’ Company tested silver items. If an item passed, it received the king’s mark, a leopard’s head. By 1478 there were many workshops in the City of London, so items were brought to Goldsmiths’ Hall for testing and marking. This gave rise to the term “hallmark.”
In 1544 the Goldsmiths’ Company adopted the king’s mark as its town mark, and today the leopard’s head is the internationally recognized hallmark of this office.
Precious metals are usually alloyed to improve hardness. Hallmarks show the metal’s fineness in parts per thousand and also include a maker’s mark and a date letter.
The Assay Office remains at Goldsmiths’ Hall and operates two satellites: Greville Street in Hatton Garden and a secure facility at Heathrow Airport for imported items. It offers many services to the jewelry trade and enforcement authorities, including:
- Hallmarking and testing
- Nickel testing, antique dating, non-destructive analysis
- Plating thickness measurement and melt/assay of scrap metal
- Jewelry valuation, laser marking
- Trading standards help, high-quality photography
- Training, seminars and events
This page was last edited on 2 February 2026, at 18:42 (CET).