2.25" from mid-1950s. Metal back has bar pin at center. Metal back is very slightly bulged outward where the shaft of the pin is inserted behind the metal through a pair of cut-outs. This causes no problem at all but is mentioned for total accuracy. The front of the piece has some faint hairline scuffs on the left side but near invisible unless caught in reflected light. The button still displays Mint and glossy. A rare local issue rarely seen.