There were no British Sovereigns issued during the 18th Century.
A British 1918 Sovereign (minted in Ottawa), uncirculated and in absolute mint condition could fetch up to £175 GBP. If it has been circulated but still in good condition, it might fetch up to £120 GBP.
A British 1918 Sovereign (minted in Bombay), uncirculated and in absolute mint condition could fetch up to £110 GBP.
A British 1918 Sovereign (minted in Melbourne), uncirculated and in absolute mint condition could fetch up to £100 GBP.
A British 1918 Sovereign (minted in Perth), uncirculated and in absolute mint condition could fetch up to £100 GBP.
A British 1918 Sovereign (minted in Sydney), uncirculated and in absolute mint condition could fetch up to £100 GBP.
A reputable coin dealer will be able to give a more accurate valuation.
$30
Other than British gold coins such as the Half-Sovereign, Sovereign, etc., Australia has never produced "Australian" gold coins for general circulation in Australia. The Sovereign coinage minted for Britain were minted to the British pattern from gold mined in Australia and were minted at either of the Melbourne, Perth or Sydney Mints (Mintmarks M, P or S respectively).
George Cotzias was born in 1918.
George Coșbuc died in 1918.
George Fiske died in 1918.
George Goldner was born in 1918.
George A. Sheehan was born in 1918.
George Matanzima was born in 1918.
George Paskvan was born in 1918.
George Bent died in 1918.
George Bunn died in 1918.
George Croonenberghs was born in 1918, in USA.