Don in SJ said:Sorry, but even with your photo and with the weight and diameter, it is impossible to say with any certainty what the copper is. The problem being there were so many lightweight, undersized King George III and King George III Irish Halfpence coppers made that it most likley could be one of them, and perhaps it if were mine and I took every measure possible to see ANY design or lettering, than I would label it as a KGIII ? (Or what it appears to be -Blank Copper)
Very few of the old coppers that are regal are close to those measurements, and to say it is one of those would be pure conjecture.
Blank coppers are nice to find! NOT, maybe take a brass brush to it and see if you see any details whatsover.
I believe for those of us fortunate enough to live in areas where the old coppers are found have all found blanks at one time or another. Those colonial era coppers were in circulation for a long time, one reason most William III coppers are almost blank in general. It is not a William III btw.
The buckle is as others have said, a common harness buckle, most probable.
Don