The Australian one ounce silver piece (abbreviated as 1 oz and designated with Ag for "silver") is a bullion coin format. Uniquely, in Australia there are two mints independently 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.
The Australian Koala series by the Perth Mint comes in several sizes and compositions: 1 kg silver, 5 oz silver, 1 oz silver numismatic (proof, high relief) and 1 oz silver bullion. The Royal Australian Mint also issues silver Kookaburra bullion coins.
The reverse design changes every year, always featuring a koala - one of the most famous and distinctive animals native to Australia. The silver ounce coins have a face value of 1 dollar, but this is only symbolic - as the bullion value of their precious metal content is much higher. The coins were .999 fine silver until the 2018 edition, which increased in purity to .9999 silver. The overall weight is slightly more than an ounce, so that the pure silver content is exactly 1.000 ASW (troy ounce Absolute Silver Weight).
The Mint says about the coin:
"The koala is loved by Australians and overseas visitors alike for its endearing bear-like appearance and soft grey fur. Each year we celebrate this adorable marsupial with highly anticipated original artistry.
Exemplifying the art of high relief minting, this coin provides Australian koala collectors with a superb opportunity to appreciate the intricacies of the 2018 design with stunning clarity. The coin is struck from 1oz of 99.99% pure silver with a proof quality finish comprising elegantly frosted design elements on a shiny, mirror-like table.
An extra thick blank and deeply engraved dies are required to press this special kind of release. The finished coin features a slightly concave table with an appreciably raised relief showcasing the design in spectacular style." | 
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