Yes, Robert, these are some of the photos that I referred to. Also, there are photos of U-505 (I think at Portsmouth) but they're not so clear - maybe a look at original copies (i.e. before being "shrunk" as part of being scanned or converted to digital format) would show the screws more clearly.

Particularly, the later photos of U-505 show what looks like a "bite mark" taken out of the right screw.

But the original question was asked by von Schoenvorts so I'm thinking that he's following these leads.

Best regards, B Henderson NC USA