A coin issued by an official or original entity. Authentic indicates it is not a replica or counterfeit coin. 

Au

Elemental (scientific) abbreviation for gold.

Blank

Applied to a piece of metal before it is struck by the dies to convert it into a coin.

Bullion coin

Coins made of a precious metal and traded at current bullion prices, or at a small premium over bullion. Bullion value of a coin is used at or close to its intrinsic metal value.

Bust

Portrait on a coin, usually displaying the head, or head and shoulders of an honoured person.