With the possible exception of traders tokens (with the traders business name on them), there were no "Australian" halfpennies minted prior to 1911.
There were was no Australian 1956 Halfpenny minted.
The last Australian Halfpenny was minted in 1964.
The last Australian Halfpenny was minted in 1964.
The last Australian Halfpenny was issued in 1964.
The Royal Australian Mint produced no Australian Halfpenny coins from 1956 to 1958 inclusive.
The Royal Australian Mint produced no Australian Halfpenny coins from 1956 to 1958 inclusive.
There were no Australian 1937 Halfpennies minted.
There were no Australian Halfpennies minted from 1956 to 1958 inclusive.
There were no Australian Halfpennies minted from 1956 to 1958 inclusive.
There is no Australian 1921 Halfpenny with a spurious "E" on it. You may have a genuine oddity. A reputable coin dealer will be able to assist with verification and give a valuation.
An Australian 1942 Halfpenny minted in Melbourne, has no mintmark. An Australian 1942 Halfpenny minted in Perth has a dot (.) after the (Y) in PENNY (PENNY.). An Australian 1942 Halfpenny minted in Bombay has an (I) below the King's head.
With the possible exception of traders tokens (with the traders business name on them), there were no "Australian" halfpennies minted prior to 1911.