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

Australia's platinum koala series launched in 1987, making Perth one of the earliest sovereign mints to issue a dedicated investment bullion program in platinum. The annual design change on the reverse was a deliberate marketing decision to drive collector demand alongside bullion buyers — a strategy borrowed partly from the Canadian Maple Leaf's success but differentiated by varying imagery rather than a static design.

Ian Rank-Broadley's fourth portrait of Elizabeth II, introduced across Commonwealth coinage in 1998, first appeared on this series during this exact two-year window.