A hallmark is a mark stamped onto items made of Gold, Silver, Platinum and Palladium to certify the fineness and standard of purity of the precious metal. The item is first assayed at one of the UK's four assay offices, this is a process used to verify the metal content.
Hallmarking is a legal requirement in the UK with the exception of items that are under the weight exemptions listed below.
• Silver 7.78 grams • Palladium 1.0 gram • Gold 1.0 gram • Platinum 0.5 grams
You will also find the London Hallmark on many Sally Lacock Pieces that fall below the exemption weight as it guarantees the authenticity and provenance of the piece, carrying the makers mark, date mark, assay office mark as well as the fineness mark and she feels that it becomes an important part of the item's history. If an exempt piece is not hallmarked this is usually because the process would not suit the form
The Four Assay Offices in the UK
This mark indicates the particular Assay Office at which the article was tested and marked.
The Date Mark
A non-compulsory mark, the date letter changes annually on January 1st. The font, case, and shield shape all change so each can only indicate one specific year. The assay office have all date punches destroyed at the end of the year.
More in depth information about hallmarking can be found at the Assay Office