The Pilot's Corsair, Part IV, A Manual for Operating the F4U-1, F3A, & FG C-130 The knobs are stiff but

The knobs are stiff but rotate

it could easily fit in the pocket of a mariner for determining position at sea or for determining horizontal positions on land

This direct-reading magnetic compass module was used in the "Wimperis" Course-Setting Bomb Sight of the British Royal Air Force

Included are:

according to the US Army Air Force's Interchangeability Cross Reference Chart dated Feb 1945

The Pilot's Corsair, Part IV, A Manual for Operating the F4U-1, F3A, & FG C-130 The knobs are stiff butThis is an original 18 page typewritten, 8. 5x11" pamphlet prepared by the USNAAS Green Cove Springs Florida for training pilots on the USN Fighter Corsair, dated May 1945. It is Part IV in a series and includes Section 11. Survival Equipment and Section 12. Armor and Armament.