For those who also collect varieties, here are a few:
5 cents 1966 Canberra Mint (left picture) with a short spine on the right shoulder of the echidna.
5 cents 1966 London Mint (right picture) with a much larger spine there:
And 20 cents 1981 with many thanks to our Australian friend brismike who pointed me at this variety:
20 cents 1981 Canberra Mint (left picture) with 4 full and thick claws of the platypus under the 2 of the 20
20 cents 1981 Winnipeg Mint (right picture) with 3 full and thin claws and 1 half claw there:
Change requests are made.