For an expert: What kind of mouthpiece did John Coltrane use on his tenor?

I think its metal but I cant tell. All I do know is that I need a new mouthpiece and dont know what to get. I would love to get a sound like Coltrane's or Archie Shepp's mouthpieces did.

I can't be sure, but maybe,
Selmer BA # 28,xxx, Selmer MK6 #56,xxx.....
I'm pretty sure he used a variety to get the right mix.

Coltrane played Metal Otto Link mouthpieces almost exclusively.. (as exclusively as any sax player sticks with one type of mouthpiece)
From everything I've read, he had a LOT of these (like a suitcase full)... with a lot of custom work done on them by himself, and by other mouthpiece refacers.. he was always searching for "that" sound.
On Soprano, he played a Metal Selmer E

Archie Shepp also played Metal Otto Link pieces.

I have seen album covers with him playing what looks like a metal Selmer D mouthpiece - I have one just like it.