Circular protractor made of cellulose-based plastic. The outer scale is marked from 0 to 180 by degree on each half, with an inner scale marked to fractions of points and the cardinal and half-cardinal directions indicated by letters (N, NE, etc.). There is a hole at the centre, with a metal finger ring around this to facilitate its use in chart plotting.

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.