The first of these seen is a highly prized variety of the 1966 issue, with a "wave" on the top of the bottom stroke of the 2 in "20" on the reverse face.

Other varieties of the reverse face generally involve the length and number of the claws of the platypus.

Due to differences in the milling and annealing process, the Canadian variety of the 1981 20-cent coin is distinctive to attentive collectors and even cash handlers.

The top and bottom edges of the milling is rounded over, not squared like the Australian and London varieties, and despite being in circulation for well over 25 years, even when well worn, the fields remain shiny, and not dulled like those produced at other mints.

Significant premiums have been paid for a small number of mint rolls from these years that have shown up in auctions.