I have a Sterling Mag Housing 'Blank'. It has never been fitted to a receiver, has all the nomencleture stamped on it. EXCEPT a Serial Number, & has not been drilled for the Screw, Mag, Catch........It is an uncontrolled item in the UKicon as it is. VERY unusual to encounter one of these, unless you worked at the now Defunct Sterling Factory that was at Dagenham.