2500 Dollars - Elizabeth II 6th Portrait - Jewelled Koi

Perth Mint's "coloured gold" technique — used here to produce the rose and white gold koi inlaid directly into the field — was developed in-house and remains one of the few minting processes globally that integrates differently alloyed gold into a single coin without plating or surface application. The rose gold achieves its colour through a copper-gold alloy at approximately 75% purity; the white gold through a palladium or nickel mix at comparable fineness.

The 10oz .9999 fine gold base already places this at the upper end of Perth's standard bullion-luxury crossover range. The additional inlaid alloys are calculated separately in the composition, which is why the specification reads as three distinct metal entries rather than a blended figure.