Reference No. 13/88. By J. A. Nicholl & Co. 1944 dated. 'Capt. Field's Improved' boxwood parallel rule with brass fittings. Approximately 45cm/18" in length x 7.5cm/3" wide when closed. Small but clear Air Ministry and crown markings. Minor scratches and 'bumps' around the edges but in very good used condition. As used by the Navigator for route plotting in bomber aircraft. Unusual manufacturer. Stock code M22422.