The coins of the Australian dollar were introduced on 14 February 1966, although they did not at that time include the one-dollar or two-dollar coins. The dollar was equivalent in value to 10 shillings (half a pound) in the former currency. Regular coinage Produced by the Royal Australian Mint, all current coins have featured four versions of the effigy of Elizabeth II, former Queen of Australia, on the obverse. The first effigy was designed by Arnold Machin, the second effigy by Raphael Maklouf, the third effigy by Ian Rank-Broadley and the fourth effigy by artist Jody Clark. They have all been matched with designs by the Australian-born artist Stuart Devlin on the reverse. The set now comprises a 50c, 20c, 10c and 5c coin, all still referred to as "silver", although they consist of 75% copper and 25% nickel. For many years there were also 2c and 1c coins, traditionally called "copper" coins, although they are actually an alloy of copper and zinc. The original 50c coin was circular and contained 80% silver and 20% copper, and the metal in the coin quickly became worth more than 50c. It had almost identical dimensional specifications to the British half crown coin. However, to avoid confusion with the 20c coin, and because of its excess value, it was only produced for one year and then withdrawn from circulation. No 50-cent coins were minted for 1967 or 1968. The coin was issued in a dodecagonal (12-sided) shape starting in 1969, although the 12-sided version had been minted in 1966–67 as a specimen piece, to test the design. The standard design 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, although the coin has been issued with both standard and commemorative designs. The dodecagonal version has a mass of 15.55 g and a diameter of 31.5 mm, and the round silver version had a mass of 13.28 g and diameter of 31.5 mm. 94.13 round 50c coins make up a fine kilogram of silver. "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. They have content of 2% nickel, 6% aluminium and 92% copper. The two-dollar coin is smaller