Jewellery hallmarking, or "stamping" was created as a way to notify buyers of the purity level of the gold or silver they are purchasing to prevent unscrupulous merchants from claiming that their gold or silver was more valuable than it really was. Other stamps are used to denote jewellery designers and manufacturers.
In gold jewellery, a stamping of 24 kt or 999 means that it is 100 per cent pure gold, 18 kt or 750 means that is 75 per cent pure gold, 14 kt or 585 is 58.3 per cent pure gold, and 10 kt or 417 is 41.6 per cent pure gold.
A stamping of 925 in silver jewellery means that it is sterling silver and contains 92.5 per cent pure silver, with the rest being other metals such as copper. In European jewellery, it is also possible to see hallmarks such as .800 or .813 which also indicate the percentage of pure silver in the piece.
Gold Plated Marks
If a piece of jewellery is gold plated rather than solid gold, it will often be marked with HGE, which means Heavy Gold Electroplate.
Gold Filled Marks
Gold filled items will often be marked with a stamping such as 1/10 18kGF. This means that there is an 18kt gold layer on the outside of the jewellery piece that weighs 1/10th of the total metal in that item.
Platinum jewellery that is at least 95 per cent platinum will be marked with a PLAT or PT950. Pure platinum is often noted with a PT1000.