This 1913 sovereign is slightly more 'orange-gold' in colour than the normal 'yellow-gold' coin at that time.
I am not sure why this is:
I can present a few facts and the reader can then make up their mind as to why out of all of the gold sovereigns that have passed through my hands why this coin is different in colour to all the rest.
Gold sovereigns are not made out of 24 carat gold as making them in pure gold meant they were softer and wore more easily. i.e. shorter life.
To get the sovereign down from 24 carat to 22 carat gold from 1817, when the standard sovereign as we know today in weight and carat were first made - the pure gold was mixed with silver to get 917 parts of gold to 83 parts of silver or other metals !
I understand that adding silver made the gold more 'yellowish' and adding copper gives a browner more orange colour.
I understand that over the century 1817-1917 several experiments were made to try and improve the wear of the sovereign and that copper was also added to the gold mix.
Is this one of those occasions when maybe more copper was added !?
Whatever the answer - the coin is in EF condition and is attractive in its colour and appears to be a one off - for now !