Could that be a hammer to fit someones stub that only has one hand
Best I could come up with anyway.
Ken
Bloody hell Ken, you're on fire today!

Yes indeed, it's a hammer made to fit onto a prosthetic arm in place of the false hand. I imagine it was always wise to remember what tool was fitted at the time, the combination of a craft knife and crotch itch not being a happy one.
GC