It’s a real proto-Leatherman, isn’t it? I suspect that the strange offset bar holding the socket also had a significance, but what? Maybe it allowed for only turning a nut in one direction? Or for turning a nut set in a curved cut-out?

I like Anon’s suggestions, though I suspect that ground- rather than aircrew would have carried a tappet adjusting tool. Perhaps it really is a ******itsjammednowhowwillIgetthatSchpitfeuroffmeinarschschlussel?

Adrian