25 Dollars - Elizabeth II 4th Portrait - Koala - Platinum

Australia's platinum Koala series, which Perth launched in 1987, was one of the earliest national bullion programs to use platinum as its primary metal rather than as a premium variant of an existing gold or silver issue. The annual design rotation — the koala motif changes each year — was a deliberate strategy to cultivate collector demand alongside pure bullion buyers, keeping the series commercially viable through platinum's notoriously volatile spot price swings of the late 1990s and early 2000s.

The 2004 issue appeared as platinum was climbing out of a trough toward the historic highs it would reach by 2007, briefly overtaking gold by a factor of nearly two.