A) Looking at the picture, I don't see any metal plate covering a part of a wooden bench. I see what I assume is a part of the bulkhead
B) Was this Simpson fellow on the Slater, or was he on one of the other ships? The story is told in a very complicated way, making it hard to tell. If he wasn't on the Slater, why is the ship he DID serve on unnamed? He doesn't remember what ships he served on?
C) If he was on the Slater, then if the plate is there, what's the problem? If he wasn't on the Slater, that would explain the absence of the metal plate, but that doesn't do anything to prove that this ship is or isn't the Slater.
D) If he was on the Slater, it makes sense he was present at a crew reunion. If he found the plate, it proves the ship IS the Slater. If he wasn't on the Slater, why is he on the Slater in a reunion with the Slater crew?
There are some fairly large gaps and holes in that story.....