Around 16 millimeters in diameter, but it's probably more than that. I'm 98% sure that it is Hungarian. It's probably made from billon.
Depiction of an eagle. There's a text around, can't recognize most of it, but I'm almost certain that I can see “R” at eleven o'clock and “W” at five o'clock.Hungarian coat of arms,I think. Can't recognize text around it.