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 mark 125 years since the foundation of the Perth Mint.
The mint says about it:
The Perth Mint opened on 20 June 1899 at the height of the Western Australian gold rush. Refining the gold and striking 106 million sovereigns over the next three decades, it went on to produce vast quantities of Australian circulating coinage between 1940 and 1984. With an outstanding reputation for quality, craftsmanship, and efficiency, The Perth Mint returned to its original purpose as a maker of fine gold coins in 1986. Today, it is renowned for the design and production of exclusive Australian collector and investor pieces.
Reflecting its best-known contemporary coin series, the piece portrays a kangaroo, kookaburra, and koala artistically arranged among a representation of golden wattle, Australia’s national floral emblem. | 
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