The purity of the metal used in each piece of jewellery is shown by a stamp or hallmark.Platinum is 95% pure (PT950)Gold 18ct is 75% pure (750)14ct is 58.4% pure (584)10ct is 41.7% pure (417) (10ct is the minimum for some countries to be classed as gold, eg. USA & parts of Europe)9ct is 37.5% pure (375)Fine silver is 99.9% pure (stamped with a half moon shape)Sterling silver is 92.5% pure (925)