Pamphlet No.870. 'Instructions for the use of the Barr and Stroud Reflector Gunsight, Type G.J.3 or Mark III, IIIA or IIIA* for Aircraft'. P/b, approximately 16.5 x 21cm, 4pp. This type of sight was used extensively in bomber gun turrets including the Lancaster and Wellington. Some creasing and wear but good overall condition. Stock code P27183-28.