Mackaydon is right with George iii. It’s a copper alloy copy of a spade Guinea or half Guinea. They were produced in large numbers as gaming tokens. Article here:
There is an extensive series of over 1,000 different Imitation Spade Guineas, issued not in gold but in brass or bronze. Some are gilt which can make it look like gold and this does cause some confusion. They were mostly struck in the 1800's, during the reign of Queen Victoria, but to avoid the C...
Agree with 'Gaming token'. These were made as facsimiles of both spade guineas and half-guineas. The guineas were approximately 24mm diameter and the (less common) halves were approximately 20mm.