 One-dollar coins were introduced in 1984, followed by two-dollar coins in 1988 to replace the banknotes of that value, while the one- and two-cent coins were discontinued in 1991 and withdrawn from circulation.In commemoration of the 40th anniversary of decimal currency, the 2006 mint proof and uncirculated sets included one- and two-cent coins.In early 2013, Australia's first triangular coin was introduced to mark the 25th anniversary of the opening of Parliament House.