Assay office

An assay office is the body that does the testing and the striking. The UK government's hallmarking guidance lists the assay office mark as one of the three compulsory components of a UK hallmark, identifying which of the four UK offices tested and marked the article; each office also keeps the register of sponsors' marks it has approved.

In the United Kingdom the offices are supervised rather than run by a central body. The British Hallmarking Council states: "We supervise the hallmarking activities of the 4 UK Assay Offices to ensure there is adequate provision of hallmarking within the UK." Its duties include "working with the assay offices and Trading Standards to ensure that hallmarking law is enforced" and "monitoring the work of the UK assay offices and their established sub-offices". The four are the Birmingham Assay Office, the Edinburgh Assay Office, The Goldsmiths' Company Assay Office and the Sheffield Assay Office.

Switzerland, where watch cases must be marked, runs the function inside its customs administration. The Federal Office for Customs and Border Security lists the Central Office for Precious Metals Control at Brügg together with precious metals control offices at Biel, La Chaux-de-Fonds, Chiasso, Geneva and Zurich, and notes that not all of them carry out analyses or official hallmarking.

India uses a network of recognised centres rather than a few statutory offices. The Bureau of Indian Standards recognises Assaying and Hallmarking Centres, which apply to it for that recognition, and points to IS 15820:2009, "General Requirements for Establishment and Operation of Assaying and Hallmarking Centres", as the standard they work to.