The Australian one kilo silver piece (abbreviated as 1 kg 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 reverse design changes every year, always featuring a koala - one of the most famous and distinctive animals native to Australia. The silver kilo coins have a face value of 30 dollars, 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 1 kg, so that the pure silver content is exactly 1,000 grams (equal to ASW 32.151 troy ounces).
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." | 
Search for Australia: Silver Kilo 2018 Australian Koala on eBay 