What is this?

Escape button 1.JPG
Escape button 2.JPG

Yes, it's a button on a string.  But, it's really an escape button compass from the Second World War.  

Like a normal button, it was sewn on the uniform.  A solider could remove the button, which is magnetized, suspend it on a pin and a pre-determined mark on the button would face North.  Some of these buttons may have also been floated in water to achive the same effect.