A cellulose-based plastic plotting grid used in air navigation. The grid consists of a series of concentric circles with 12 radial lines. There are small holes at the intersections to allow plotting on a chart, with an inscription in the corner suggesting that it is for use on a scale of 1:10,000. The maker's name is inscribed in one corner, with the initials 'H.T.A.B.' roughly inscribed in another corner.

This is one of a number of items formerly belonging to Henry Theodore Augustus Bosanquet (1870-1959), who was a leading figure in the development of air navigation in Britain during the First World War.