(No-one seems to know what the Mk I looked like.)" "No - this is a knife..." Crocodile Dundee The Wilkinson was included in the survival packs of aircrew operating over the boonies and would be useful for building hides, making spears, chopping up jungle wildlife etc.
It has been specially designed to cater for those minor life-threatening occasions like crashes and bale-outs.
It is quite often carried by pilots of vintage aircraft as cockpits can change shape radically during a crash and strap releases might be inaccessible; just as that irritating dribble of fuel starts to run down your neck...
Worn on the leg, often inverted on the calf or thigh, the release knife is freed from its scabbard by squeezing the metal tabs on either side of the handle.
The cutting edge is actually on the inside of the curved blade, which makes it useless for knife-fighting; but very efficient at slicing through straps, hoses, electrical leads - and parachute cords should you end up dangling from a tree.
The legendary escape compass issued to aircrew during WWII was six tenths of an inch in diameter and was often concealed in a uniform button with a screw top.