Brass metal fly buttons as used on R.A.F. battledress trousers etc. Approximately 13mm diameter. One has a small 'spike' in the centre on which the second magnetised button can be balanced. Small luminous dots on this button indicate North and South. Another ingenious gadget from MI9 issued to aircrews to aid escape and evasion. Excellent condition and still sewn to the card of issue. Stock code E21869.