<P> The 50 ¢ coin originally had a circular shape, and contained 80% silver and 20% copper, so that the material of the coin was worth more than 50 ¢ . It was made to almost identical dimensional specifications as the British 2'6 pence half crown . However, to avoid confusion among the round coins, and because of its excess value, it was only produced for one year then withdrawn from circulation; there were no 50 - cent coins minted for 1967 or 1968 . It was changed to a 12 - sided shape for 1969 and all following years, but the 12 - sided issue was minted as a specimen piece in 1966--67 to test the design . It has since been issued in both standard and commemorative designs . </P> <P> The standard designs on both versions of the coin are the same: the obverse carries the effigy of the sovereign, and the reverse shows the Coat of Arms of Australia . The dodecagonal version has a mass of 15.55 g and a diameter of 31.5 mm, and the round silver version has a mass of 13.28 g and diameter of 31.5 mm . 94.13 Australian 1966 round 50 ¢ coins make up a fine kilogram of silver . </P> <P> "Gold" one - dollar and two - dollar coins were introduced in the 1980s . The one - dollar coin was introduced in 1984, to replace the banknote of the same value . The two - dollar coin, also replacing a banknote, was introduced in 1988 . These have content of 2% nickel, 6% aluminium and 92% copper . Thus, all Australian coins in use currently are composed of more than half copper . The two - dollar coin is smaller in diameter than the one - dollar coin, but the two - dollar is slightly thicker . </P> <P> The one - and two - cent coins were discontinued in 1991 due to the metal exceeding face value and were withdrawn from circulation . </P>

When did the one dollar coin come out in australia