The Australian five ounces silver piece (abbreviated as 5 oz and designated with Ag for "silver") is a bullion and commemorative 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 Australian Wedge-tailed Eagle series by the Perth Mint, and the first design by John M. Mercanti (issued in 2014 and 2015 only).
The Mint says about it:
"The Wedge-tailed Eagle is Australia’s largest bird of prey and one of the biggest eagles in the world. Found throughout mainland Australia, Tasmania, and southern New Guinea, the Wedge-tailed Eagle has a wingspan of up to 2.7 metres, and displays a long, wedge-shaped tail and feathered legs.
The coin is struck from 5oz of 99.9% pure silver in proof quality. The coin’s reverse depicts an impressive Wedge-tailed Eagle in mid-flight as it prepares to land on a tree branch.
The Perth Mint commissioned American sculptor and engraver, John M Mercanti, the 12th Chief Engraver of the United States Mint, to create the 2015 Australian Wedge-tailed Eagle design. Each coin’s reverse depicts an impressive Wedge-tailed Eagle in mid-flight as it prepares to land on a tree branch." | 
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