The 50 cent coin was first introduced with decimalisation on 14 February 1966. This original design featured the Commonwealth Coat of Arms struck on an 80 per cent silver coin. Silver prices rose above the face value of the coin in 1967 and striking of the coin was suspended in March 1968. Although it was rumoured that the Royal Australian Mint had lost money on striking these coins, all metal used in the manufacture of the 36.5 million coins produced was purchased before the price rises.
Apart from the uneconomic cost of continuing the issue of the silver 50 cents, significant negative comment arose from confusion of the circular coin with the 20 cents. The decision to reissue a 50 cent coin considered not only a change to materials but also different shapes to help solve confusion with the 20 cents. A new shape and alloy was reintroduced into circulation in September 1969. These new dodecagonal (12-sided) coins have been used since.
The composition of the 1966 coins is 80% silver and 20% copper (0.3394 ASW). They are still legal tender, although in practice they do not circulate.