hallmark
A hallmark is a legally recognised set of marks applied by an assay office after a precious-metal item has been independently tested for fineness.
Why it matters
UK hallmarking is most useful for jewellery and fabricated items described as gold, silver, platinum, or palladium. A full modern hallmark normally includes the sponsor mark, millesimal fineness mark, and assay office mark, with date letters and traditional fineness marks sometimes appearing too.
What to check
Hallmarks can be worn, partial, misread, or copied, and bullion coins and bars are often checked through mint or refiner specifications instead. Use hallmark evidence with weight, condition, paperwork, and professional testing where needed.