Australian fifty-cent coin

The twelve-sided Australian fifty-cent coin is the third-highest denomination coin of the Australian dollar and the largest in terms of size in circulation. It is equal in size and shape to the Cook Island $5 coin, and both remain the only 12-sided coins in the southern hemisphere. It was introduced in 1969 to replace the round fifty-cent coin issued in 1966.

The original, round, 50-cent coin was made of 80% silver and 20% copper; but as the value of a free-floating silver price became higher, the coin's bullion value became more valuable than its face value; so that version was withdrawn from circulation and replaced with the dodecagonal cupro-nickel version.

It is by diameter the largest Australian coin currently issued and second largest after the Crown of 1937–38. It is also the heaviest Australian coin in common circulation. Many commemorative designs have been issued, the large size allowing for detailed content.

With a diameter of 31.65 millimetres (1.246 in) across flats, the 50-cent coin is one of the largest in volume among those currently circulating in the world. Coins of larger diameter include the Costa Rican five-hundred-colón and the old fifty-franc (CFP), both 32.9 millimetres (1.30 in).

The 1986, 1987, 1989, 1990, 1992, year dated 50¢ are only available in mint and proof sets, with the exception of the 1967 and 1968, as no mint/proof sets exist for those years and there were no circulation strikes produced either.

Fifty-cent coins are legal tender for amounts not exceeding $5 for any payment of a debt.