By Aston & Mander & Co. London. 1942 dated. '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/marking and some damage/loss around the edges close the the ends. Reasonable condition. As used by the Navigator for route plotting in bomber aircraft. Stock code M19219.