100 Dollars - Elizabeth II 4th Portrait - Koala - Gold Proof coin

Australia's koala gold series, managed by the Perth Mint rather than the Royal Australian Mint, operates outside the standard currency framework — these are legal tender pieces issued under the Currency Act but produced primarily for the bullion and collector market, never intended for circulation. The .9999 fineness places them among the purest gold coins in regular production anywhere, a standard Perth Mint adopted in part to compete directly with the Royal Canadian Mint's Maple Leaf program during the 1990s bullion wars.

The 4th Portrait of Elizabeth II, sculpted by Ian Rank-Broadley, was introduced on Australian coinage in 1999 and remained current until the transition to Jody Clark's effigy.