Such a coin does not exist.
The 1898 British Half-Sovereign was only ever minted at the Royal Mint London.
The only "Australian" Sovereigns were minted at the Sydney Mint between 1853 and 1870. These have "SYDNEY MINNT" and "AUSTRALIA" clearly inscribed on the reverse. Any other Sovereign circulating in Australia would have been a British Sovereign minted to the British pattern. These may have been minted in either the London, Melbourne, Perth or Sydney Mints.
The last British Shilling minted for general circulation was minted in 1966.
The last British Florin minted for general circulation was minted in 1967.
There were no British 1800 Halfcrowns minted.
There was no 1805 British Halfcrown minted.
There were no 1830 British Halfpennies minted.
There were no 1832 British Halfpennies minted.
There was no 1946 British Crown minted.
Such a coin does not exist. The last British Halfcrown coin minted for circulation was minted in 1967. The last British Halfcrown Proof coin was minted in 1970.
The last British Halfcrown was minted in 1970.
The last British Florin was minted in 1970.
The last British Halfcrown was minted in 1970.