Flat bar type compass in a rounded diamond shape. Luminous dots to indicate North & South. There is a hole to 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 the shirt collars or jacket lapels of airmen 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 E17404.