1983 Australian 50-Cent Coin ​This is a standard circulation coin from Australia featuring the dodecagonal (12-sided) shape that was introduced in 1969. ​Obverse (Front): Features the second portrait of Queen Elizabeth II as designed by Arnold Machin. ​Reverse (Back): Displays the Australian Coat of Arms, which includes a kangaroo and an emu supporting a central shield. ​Composition: It is made of cupro-nickel (75% copper and 25% nickel), not silver. rarest coin in the world