This button was found in my yard which is the site of an old brick school built 1822. The shank, which was bent, was popper or alpha type. Possibly copper, looks press fit. I think it might be from the 1950's, what do you think?
Looks older than that, and 3 fleur de lis under a crown is the coat of arms of the french monarch. I can't tell you any more than that, buttons ain't my thing, but I'm betting someone will steer you better. Welcome to TNET.