Coins
Several nation states produce bullion coins – probably the most well-known is the South African Krugerrand. Although they are issued – nominally – as legal tender, their face value as currency is significantly below the bullion value.
For example, Canada mints the one troy ounce Gold Maple Leaf, which has a face value of $50, but has a bullion worth around $750 (as at January 2008). The minting of coin by national governments is designed towards certification and indeed numismatic value.
Gold Purity
The purity of gold coins will vary – 99.9% purity is a common value. Normally, a coin will contain a given quantity (eg 1 troy oz) of the alloy – however the South African Krugerrand contains exactly one ounce of gold, the impurity increasing the coin’s actual above an ounce.