Something else collectors should be aware of is Australian pre-decimal silver coins dated 1910 to 1945 are sterling silver and 50% silver 1946 to 1964.
When it comes to Australian coins true penny’s are the predecimal coins so that means they must have a date of 1964 or earlier. The decimal 1 cent coins that are not called pennies have dates from 1966 onwards. Regular 1975 and 1976 1 cent coins do not have Mintmark’s