Cellulose-based plastic protractor. The semi-circular scale is marked from 0 to 90 by degrees in two quadrants. The maker's name is inscribed along the bottom, with the intitials 'H.T.A.B.' roughly inscribed beneath.

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.