This is really interesting. So I guess that's what briar looks like after it's been soaking in freezing sea water for decades.
the band looks like it's rusted, so that rules out a number of precious metals.
I figure though if you can't actually read the maker's mark, then it's just guess work. If it can be determined that the mark actually IS a maker's mark, then that would narrow it down a bit, I think.
If I was seriously researching this, I would find out where in the wreckage the pipe was found, and find out if that location can be cross-referenced with the passenger manifest.
The passenger manifest would tell you the most likely country of origin of the owner, certainly, which is a little more information to help narrow down the list.