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 (by Stuart Devlin) which has not been changed since its introduction, the denomination is also often used to issue circulating commemorative coins with various reverses. It is one of the heaviest coins in regular circulation in the world.
Apart from the circulating coinage, the Royal Australian Mint has an extensive program issuing 50 cent coins for collectors (Non-Circulating Legal Tender, or NCLT). Some of them - such as this one - are round, as reference to the original format of the denomination.
This coin was issued as part of the 1999 Masterpieces in Silver - Coins of the 20th Century: Memories six-coin set, highlighting important times in Australian history (mintage limit 15,000, issue price A$125.00). The reverses of each coin show a historic Australian coin design, in mirror-finish proof; the denomination and value are on the obverse.
The five cents coin depicts a 1939 kangaroo-type halfpenny.
The ten cents coin depicts a 1930 penny.
The twenty cents coin depicts a 1942 threepence.
The fifty cents coin depicts a 1918 sixpence.
With only 915,000 of these coins minted, it is a key date in the series. Interestingly, the same reverse design was used on all sixpences minted between 1910 and 1963.
The one dollar shows a 1940 shilling.
The two dollar coin shows a 1920 sovereign.
These coins are Non-Circulating Legal Tender (collector issue); composition: fine silver (99.9%). No coins of this type have been released into circulation.