It might have been some kind of improvised device. Might even have been something the French Resistance set up and he got it by mistake.
We might be able to tell by the shape of the screw heads. I’m fairly sure the 1940s era screws and the 2012 era screws would look different. These look pretty modern.
I think the ‘casket parts’ comment was probably fairly close to the winner here.
I still don’t think you’re totally out of the running, but I don’t think this guy would only be mentioning pain in the knee if all this was in there for 60-70 years.
Thanks for the response.