Hallmarking
A hallmark is first and foremost your guarantee when buying a piece of jewellery.
A hallmark means that the piece has been independently tested and guarantees that it conforms to all legal standards of purity (fineness of the metal).
Hallmarks also guarantee provenance by telling you where the piece was hallmarked, what the piece is made from, who sent the piece for hallmarking and when it was hallmarked.