3.5" with four tiny holes on back apparently for attachment to car grille or bumper but long ago someone added 2" safety pin fastener held by a pair of .25" solder spots. Metal back has minor oxidation but cello front is totally clean with high gloss and only a trivial amount of surface wear showing in certain reflected light angles. Our last example, without pin, realized $650 in Auction #182. Only the second we've handled and displays Mint.