What does a 999 hallmark mean?

The number is parts per thousand

Fineness marks state how many parts in a thousand are the precious metal. 999 is 999 parts in 1,000, so 99.9% of the weight is gold and the rest is the alloy that gives the piece its colour and hardness. In carats that is 24ct: a carat is one twenty-fourth, and 24/24 is 99.9%.

The same number is used on more than one metal: Gold (99.9% pure gold, sold as 24ct) and Silver (99.9% pure silver, known as fine silver). The colour and weight make them easy to tell apart, and we test every item anyway.

999 gold by weight today

Is it real? Three quick checks

• Look for company. A genuine UK hallmark has the fineness number inside a shaped outline, plus a sponsor's mark and an Assay Office mark. A lone number with nothing beside it is a claim, not a hallmark.
• Watch for plating codes. GP, GEP, HGE, RG or a fraction like 1/20 12K mean a thin layer of gold over base metal. These are worth very little as scrap.
• Check with a magnet. Gold, silver and platinum are not magnetic. A pull towards the magnet means a steel or nickel core.

None of these replaces a test. We check every piece with an XRF analyser before we make an offer, so you are paid for what the metal actually is, marked or not.