The Australian half ounce silver piece (abbreviated as 1/2 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.
The Mungo footprints, in the Willandra Lakes Region World Heritage Area, are the oldest preserved footprints ever found in Australia and the largest set of ice age footprints in the world.
The footprints were discovered in 2003 when the shifting sand dunes revealed the petrified indentations to archaeologists undertaking a survey of the area. Further digging and research revealed one of the most intriguing and intact insights into how people lived, travelled, hunted, and survived in the Pleistocene era during the last ice age. In 2006, the tracks were covered again by sand to protect them from the elements. Only a handful of people know the exact location of these wondrous footprints in time.
The mint says about the coin:
"The Mungo footprints walk to us across twenty millennia, from the Dreamtime itself, as a symbol of our First People’s longevity and perseverance in this ancient land. Discovered at Willandra Lakes in Mungo National Park in 2003, the preserved footprints give us an evocative glimpse of how we lived, travelled, hunted and survived in the Pleistocene era during the last ice age. With this beautiful 2021 $1 Fine Proof Coin the Royal Australian Mint celebrates the Willandra Lakes Region and its astounding footprints in time." | 
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