During the Second World War, escape compasses were an important piece of equipment developed by MI9, MI9 was a section of the British Military Intelligence that developed tools to assist with escape and evasion.
These compasses were produced in a vast variety and issued as part of escape kits, hidden in uniforms, in buttons or inside innocent looking everyday items. Under the auspices of MI9, 2,358,853 compasses of various designs were distributed during the Second World War.
A fly-button compass consisted of two trouser fly buttons: the lower one had a pivot; the upper one was magnetized.
Physical description: A button compass consists of two, bowl-shaped buttons, both brass-coloured with four holes. One button has a small pin soldered onto the back in the centre. The other button has a small depression in the centre and is designed to balance on top of the pin.
Brass metal fly buttons were used on Royal Air Force (RAF) battledress trousers. They were approximately 3mm diameter. Small luminous dots on this button indicate North and South.
This radio luminescent escape and evasion button compass was used by the RAF during the Second World War. It was a clever enough idea that compass buttons are still produced today!