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 issued by the Perth Mint commemorates the 100th Anniversary of the End of World War I in 2018.
The Mint says about it:
The bloodshed of World War I ended in 1918 at the 11th hour of the 11th day of the 11th month. To mark the cessation of hostilities 100 years ago, The Perth Mint offers this carefully considered numismatic tribute honouring the courage and sacrifice of those who suffered the conflict’s unremitting brutality at Gallipoli, in the Middle East and on the Western Front. The coin is meticulously struck from 1oz of 99.99% pure silver to our renowned proof standard combining a mirror-like polished background with delicately frosted relief. | 
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