Escape Kit ... my father showed me a couple of metal uniform buttons [of the plain persuasion, such as 'braces, for the attaching of', he had had in WW2. When one was placed on top of the other, there was a small dimple in the centre of the lower one that provided the pivot for the top [magnetised] button to stagger its way to pointing north. I'm not sure, but I think the 'needle' button also had a small dot of luminous paint at "N".