The Hallmarking Act
For the manufacture of jewellery and silverware, precious metals are not used in their purest forms. Instead they are alloyed with other metals. It is not possible to discern by sight or by touch what the precious metal content of an alloy is. Our customers can rest assured that all our products come with a guarantee of the precious metal content through the 700-year-old practice of third-party independent hallmarking. The 1973 Hallmarking Act makes it unlawful to describe an item over a certain weight as gold, silver, platinum, or palladium without an independently applied hallmark.
All silver articles weighing more than 7.78 grams must be hallmarked.
Gold articles weighing more than 1 gram must be hallmarked.
All platinum articles weighing more than 0.5 grams must be hallmarked.
All palladium articles weighing more than 1 gram must be hallmarked.
Articles below these exemption weights maybe described as Gold, Silver, Palladium or Platinum without the need of a hallmark.
Dealers Notice - Assay Office (theassayoffice.com)