By J.A. Nicholl & Co. 1944 dated. Ref. No. 13/88. 'Capt. Field's Improved' boxwood parallel rule with brass fittings. Approximately 45cm in length x 6.8cm wide when closed. Clear Air Ministry and crown markings. Light scratches and a few minor 'bumps' around the edges. The left end does not close as tightly as the right but in good '+' used condition overall. As used by the Navigator for route plotting in bomber aircraft. Stock code M22470.