Cant find any reference to Heminway! Most likely a gun made for an Ironmonger[ Hardware store/ gunshop]You should be able to determine souce of manufacture from the proof marks,[ Most likely Birmingham ].
Heminway/ Vs; Purdey, would compare as a basic N.A. auto; to a Rolls Royce, assuming both are in good condition and safe working order!


Roy Hebbes