J. Purdey & Sons: a scarce second pattern Norman Aerial Gunnery Sight set, comprising fore-sight

J. Purdey & Sons: a scarce second pattern Norman Aerial Gunnery Sight set, comprising fore-sight with red bead on a moving stem liked by two articulated arms to a wind vane, marked '100 MPH ON 18" ' and 'J. PURDEY & SONS.'; and a back sight with two concentric rings, marked 'A-100 MPH ON 19. INS.'. [2]

The George Geear Collection

Of significant Great War military aviation interest, this innovative sighting arrangement for aircraft-mounted machine guns was one of many contributions made by Purdey to the war effort. The concept originated with Professor Norman of Cambridge University and the design was refined and brought into production by Purdey's factory manager Ernest Lawrence. These sights were fitted to an observer's Lewis gun, and the action of the wind vanes on the fore-sight provided an automatic aiming correction to compensate for the speed of the aircraft. Ref. Dr Nicholas A. Harlow, HBSA Journal.