Hallmarking, which has been carried out in the UK for nearly 700 years, represents the earliest form of consumer protection.
Hallmarks are small markings stamped on gold, silver and platinum articles. A hallmark means that the article has been independently tested at an Assay Office and guarantees that it conforms to all legal standards of purity (fineness).
Modifications to the Hallmarking Act, effective from 1 January 1999, have changed the way articles made of precious metal are hallmarked. A UK Hallmark now comprises three compulsory symbols:
Sponsor's or Maker's Mark
Indicates the maker or sponsor of the article. In Britain, this mark consists of at least two letters within a shield, and no two marks are the same.
Metal and Fineness (Purity) Mark
Indicates the precious metal content of the article, and that it is not less than the fineness indicated. Since 1999, all finenesses are indicated by a millesimal number (e.g. 375 is 9ct). This number is contained in a shield depicting the precious metal.
Assay Office Mark
Indicates the particular Assay Office at which the article was tested and marked. There are now just four British Assay Offices: London, Birmingham, Sheffield and Edinburgh, although there were other Assay Offices in former times.
Traditional Fineness (Purity) Mark
Prior to 1999, silver and platinum finenesses were indicated by symbols.
Common Control Mark
This is a mark used by countries which are signatories to the International Convention on Hallmarks.
Until 1999, a date letter indicating the year of hallmarking was compulsory. This is no longer the case, but it can be applied voluntarily in addition to the compulsory marks.
These marks have been stamped to mark significant occasions such as Royal Jubilees or anniversaries. One example is the Millennium Mark which was applied to precious metals during 1999 and 2000.