Air Ministry 'Douglas' Combined Protractor & Parallel Rule. Stores reference 6B/47. Perspex, approximately 12 x 12cm. Marked with a grid and compass bearings around the edges. A. Crown M. marked. One corner has a piece missing and the perspex is a bit 'fogged'. Comes with a second example - this one has some 'warping' at the edges. Complete with original card sleeve printed with instructions. As used by the aircrew navigator. Stock code Prot1.