Australian 20 cent coins since the introduction of Decimal Currency in 1966 are still in circulation, so unless they are part of a proof set or as previously described, they are worth 20 cents.
The only slightly unusual thing about the 1981 coins was that, for the first time in years, Australian Coins were minted outside of Australia. Aproximately 15-20% were minted in Wales and Canada.
There is however an error coin dubbed 3.5 claw that can go for 100's AUD. There may be other error coins as well that will increase it's value beyond it's face value.
James Cook does not appear on any Australian or New Zealand 20 cent coins.
There is no Australian "cent" from 1939. Decimal currency was introduced in Australia in 1966.
There is no Australian "cent" from 1938. Decimal currency was introduced in Australia in 1966.
Such a coin does not exist. The Australian "cent" coins were first introduced in 1966.
Decimal currency was not introduced into Australia until 1966. There is no such thing as an Australian pre 1966 cent.
There is no Australian 1954 20 cent coin. Decimal currency was introduced in 1966.
There is no Australian 1950 20 cent coin. Decimal currency was introduced in 1966.
Such a coin does not exist. The first Australian 20 cent coins were issued in 1966.
Such a coin does not exist. There were no Australian 1967 50 cent coins minted.
Such a coin does not exist. The first Australian 10 cent coin was issued in 1966.
Such a coin does not exist. The first Australian 20 cent coins were issued in 1966.
The Australian 2 cent coin was introduced at the changeover to decimal currency in 1966. There were no Australian "cent" coins minted prior to 1966.