The Australian 50 cent denomination was first introduced as a silver coin with decimalisation on 14 February 1966, but was changed in 1969 to its current specifications: a large dodecagonal (12-sided) copper-nickel coin; apart from the usual design featuring the Australian Coat of Arms, the denomination is also extensively used to issue circulating commemorative coins with various reverses. It is one of the heaviest coins in regular circulation in the world.
Apart from circulating coins, the Royal Australian Mint has a range of Non-Circulating Legal Tender (NCLT) 50 cent coins issued for collectors, such as this one.
This coin was issued as a companion coin to the Koala bullion series by the Royal Australian Mint (not to be confused with the Australian Koala by the Perth Mint).
The mint says about it:
"An endearing mother and baby koala feature on this uncirculated coin as part of the Royal Australian Mint’s second release in its Koala Series. The 50c product is new to the 2025 release and is presented as a coin in card. Available in Australia only, this coin will be valued by wildlife lovers and entry level collectors."
No coins of this type were released into circulation. | 
Search for Australia: Fifty Cents 2025 Koala on eBay 