The Australian half-ounce gold piece (abbreviated as 1/2 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.
This coin is part of the long-running Australian Kangaroo bullion coin series by the Perth Mint.
The mint says about it:
The Red Kangaroo, the world's largest marsupial, is renowned for its remarkable agility, capable of speeds of almost 50kph. This unique bullion coin series pays tribute to the country's definitive animal emblem that traces its roots back to the Guugu Yimithirr word "gangurru". From the arid interiors to the lush bushland parks on the outskirts of cities, kangaroos inhabit every corner of this wide, brown land. Embrace this emblem of Australia and join in celebrating one of Australia's most famous marsupials. | 
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