By Aston & Mander & Co. ( Est. 1789) London. 1944 dated. 'Capt. Field's Improved' boxwood parallel rule with brass fittings. Approx. 45cm/18" in length x 7.5cm/3" wide when closed. Clear Air Ministry and Crown markings. A bit grubby and faded and with very minor wood loss/chips at the edges in places. Tarnishing of metal parts. Good used condition overall. As used by the Navigator for route plotting in bomber aircraft. Stock code M18083.