Congratulations if you have one, but Australia was discovered in 1770 and the 50 cent coin was not introduced until 1966.
You possibly refer to the 1970 Australian 50 cent coin which commemorates the bicentenary of the discovery of Australia by Captain Cook in 1770.
These coins are potentially still in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth 50 cents.
The first Australian 50 cent coin was issued in 1966.
Please check your coin.
Australia had only just recently been discovered in 1776 and the first Australian 50 cent coins were issued in 1966.
Such a coin does not exist. The first Australian 10 cent coin was issued in 1966.
Such a coin does not exist. The Australian 2 cent coin was first issued in February 1966.
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 20 cent coins were issued in 1966.
Such a coin does not exist. The Australian "cent" coins were first introduced in 1966.
Such a coin does not exist. The Australian 2 cent coin was first issued in 1966 on the introduction of decimal currency.
Such a coin does not exist. The Australian 1 cent coin was first issued in 1966. The Australian One Penny coin was issued from 1911 to 1964 inclusive.
Such a coin does not exist. The first Australian 2 cent coin was 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.