Air Ministry and M19 issued concealed button compass for aircrew. This half-inch diameter rotor compass was issued to RAF and RCAF aircrews. Early types had four holes in the rotating bezel, and the later ones had a star-shaped pointer. Used by aircrewmen in the event of a bail out or to escape or evade the enemy when in occupied territory. The button was made with either left or right hand thread after the first types were discovered by German captors. When unscrewed this button contains a small rotor compass. This type of escape compass was introduced as early as 1940 but ceased to be used after the introduction of the battledress later in 1941.
Brass, glass, mineral oil, magnet