1770-1800 British 1-piece copper Civilian style Coat button. These are called “alpha” shanks (See Tice pg. 3 & 9), with the shank protruding 6 mm. These are known to have been dug at Rev. War sites, with some overlap for use with military items. (Size 36 mm). I’ve included a photo of a sample card from an old collection showing 7 similar types. These are not for sale, just shown for example.