The Australian two ounces gold piece (abbreviated as 2 oz and designated with Au for "gold") is a bullion coin format. Uniquely, in Australia there are two mints authorised to strike legal tender: the Royal Australian Mint (which also makes the country's circulating coinage) and the Perth Mint which only makes collector and bullion coins, as well as other bullion products.
Both mints endeavour to create coins with attractive designs, and to introduce new designs and themes often, in order to raise the numismatic value of the coins over the value of previous metal used.
The Mint says about this coin:
Beneath the ancient boab trees in the heart of the East Kimberley in Western Australia’s far north, the world’s rarest diamonds were formed more than a billion years ago. Argyle pink diamonds are a true Australian treasure, limited by nature and highly sought after by collectors and connoisseurs. Each of the Kimberley Sunset coins incorporates a superbly hand set Argyle pink diamond.
The coin’s high relief reverse and obverse are minted on concave surfaces to ensure the optimum flow of metal is achieved by the strike of the die. | 
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