A British 1931 22 carat gold Sovereign (George V)(minted in Melbourne - mintmark = M), uncirculated and in absolute mint condition could fetch up to £575 GBP. If it has been circulated but still in good condition, it might fetch anything from £165 to £350 GBP.
A British 1931 22 carat gold Sovereign (George V)(minted in Perth - mintmark = P), uncirculated and in absolute mint condition could fetch up to £200 GBP. If it has been circulated but still in good condition, bullion value.
A British 1931 22 carat gold Sovereign (George V)(minted in Pretoria - mintmark = SA), uncirculated and in absolute mint condition could fetch up to £175 GBP. If it has been circulated but still in good condition, bullion value.
The values quoted are the best possible for the best specimens in their grades, but may be significantly lower due to varying demand for the coin and the prevailing economic climate. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.
There were no British Half-Sovereign coins minted from 1927 to 1936 inclusive
I presume that you are referring to a circulated US 1931 cent with no mintmark under the date, rather than a British penny. The answer then is almost certainly under a dollar.
value of irish penny 1931
Such coins do not exist. King George IV died in 1830. King George V was king in 1931. British 1931 coins do not have any especially great (give up your job) value, but if in reasonably good condition, could get a few pounds.
The British School in the Netherlands was created in 1931.
British Pharmacological Society was created in 1931.
British Colour Council was created in 1931.
Value Line was created in 1931.
John Golding - British politician - was born in 1931.
John Sutcliffe - British politician - was born in 1931.
John Garrett - British politician - was born in 1931.
Adam Butler - British politician - was born in 1931.
The U.S. didn't mint an $1 coins dated 1931.