The data plate on this bomb sight describes it as "Bomb Sight Mark 1-A Lot No. 85 Serial No. 21, Manufactured at Edison Phono. Works Orange N.J., U.S.A."  It is the American version of a British design.  It was attached to the outside of the fuselage next to the observer's cockpit.  He could lean out, input altitude, wind and airspeed and then drop his bombs on target with greater accuracy.