The Australian two ounces silver piece (abbreviated as 2 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 two-ounce silver coin with a face value of $2 was issued as part of the Perth Mint's Lunar Series III to mark the Chinese Year of the Ox (12 February 2021 - 31 January 2022).
The Mint says about it:
"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. These 2021 coins celebrate the Year of the Ox, whose rule over every second year in the 12-year lunar cycle is said to influence people born during 1949, 1961, 1973, 1985, 1997, 2009 and 2021.
According to Chinese mythology, the order of the animals in the ancient zodiac calendar was decided with a great race across a river. Traditional storytellers say the magnanimous ox offered to carry the mouse across the water - and thus it was that on the opposite bank the diminutive creature was able to leap from the ox’s head and claim first place!
Legend has it that each zodiac animal influences the personality of the people born under its ‘rule’. Those born in the Year of the Ox are said to possess the same qualities displayed by the kind, hardworking and determined creature who first participated in the fabled event." | 
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