22.5mm and 5.0g would fit a 20¢ piece; though both the weight and composition are off. I do not know of any other us coinage that measures 22.5mm.
my question is what coin it would have been? and it came from a world coin bin in an antique shop so even the country is in question?
I don't know if this will help? It fits pretty well in this U.S. Quarter Dollar 2x2 flip. Any Ideas what this planchet would have been?
I re-measured and it is 24 mm. exact. that would explain it's snugness in the Quarter Dollar flip and re-weighted and still come up with 5.4g.