RAF tunic brass button escape compass.
These buttons were used early on during the war, when pilots and aircrew still wore their service dress tunics on Operational flights. This standard looking large button has a hidden compass inside. Ingeniously designed by Clayton Hutton and his team at MI9 this escape aid gave the airman a fighting chance to evade capture, if parachuted into enemy held territory. The compass is revealed by unscrewing the top half of the button, leaving the bottom half with the compass inside. This early example has a very fine right handed thread (later ones changed to a left hand) and the compass has a rotating disc to point North. Later escape compasses changed to a 'star' like pointer.
The button is 100% original wartime RAF issue. It is stamped on the reverse B'Ham Buttons Ltd. together with Trade Mark and a pair of cross swords.