Before revision: A Reference Card or "Romer" The War Office, Notes On Map Reading, HMSO (1940 ) is a device for increasing the accuracy when reading a grid reference from a map.
After revision: A Reference Card or "Romer" The War Office, Manual of map reading, photo reading and field sketching 1929, HMSO (1929 ) is a device for increasing the accuracy when reading a grid reference from a map.