25 Dollars - Elizabeth II 3rd Portrait - Koala - Platinum

Australia's platinum koala series, launched in 1987, was among the first government-issued platinum bullion programs in the world, competing directly with the Soviet Union's Palladium Ballerina and the Isle of Man's platinum cat issues for the attention of early precious-metals investors. The Perth Mint rotates the koala design annually, which means no two years within a series share an identical reverse — a deliberate sales strategy that transformed what might have been a straightforward bullion coin into a collector-driven annual release.

The third portrait of Elizabeth II, sculpted by Raphael Maklouf, was phased out across Australian coinage during 1998 in favor of Ian Rank-Broadley's effigy — making the 1998 date a transitional issue for this denomination.