Developed by Christopher Clayton Hutton at MI9 this is a flat bar type compass in a rounded diamond shape approximately 28mm in length. Luminous dots to indicate North and South. There is a hole at the centre to enable the user to tie the compass to a piece of thread. When hung in a glass of water the compass is steadied and will point North. These were intended to be hidden inside an airman's shirt collar or jacket lapels to provide a useful escape or evasion tool in enemy territory. Possibly not too practical given the compass is only stable in water! Very good used condition. Stock code E24308A.