The Australian ten kilograms silver piece (abbreviated as 10 kg and designated with Ag for "silver") is an extremely large and rarely used bullion 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 ten kilograms (10 kg) silver coin with a face value of $300 was issued as part of the Perth Mint's Lunar Series III to mark the Chinese Year of the Mouse, 25 January 2020 - 11 February 2021 (also called Year of the Rat).
First issued in 1995 and now in its third round, the long-running Australian Lunar Coin Series celebrates the animals of the Chinese zodiac with a sequence of annual designs portraying the mouse, ox, tiger, rabbit, dragon, snake, horse, goat, monkey, rooster, dog and pig. The mouse is the first animal in the cycle.