What gold purities or fineness levels are there?

999.9 = 99.99% (almost pure fine gold, common for bars and investment coins)

999 = 99.9% (very pure gold, also used for coins and bars)

916 = 91.6% (22 karats, e.g., Krugerrand, gold jewelry)

900 = 90% (older coins like the Double Eagle)

750 = 75% (18 karats, high-quality jewelry)

585 = 58.5% (14 karats, standard jewelry in Europe)

375 = 37.5% (9 karats, affordable jewelry, especially in the UK)