The one dollar coin circulating denomination (written as $1) was introduced in Australia in 1984, replacing the earlier banknotes. The original reverse design by Stuart Devlin featuring five kangaroos - known in Australia as the "Mob of Roos" design - has not been changed since its introduction.
The denomination is also used by both the Royal Australian Mint and the Perth Mint to issue an extensive range of collector coins, which are legal tender in Australia - such as this one.
This non-circulating $1 coin was issued to commemorate ANZAC Day.
The mint says about it:
Anzac Day falls on 25 April each year, the day Australian and New Zealand troops landed on the Gallipoli peninsula in 1915. Since 1916, it has been dedicated to commemorative activities honouring the courage and sacrifice of the first ANZACs during World War I and all succeeding Defence Force personnel who have served in times of war and other operations. | 
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