Discombobulated SOTW Member, Forum Contributor 201
Not to be telling you who is buried in Grant's tomb, but Conn made a mouthpiece that looked like that with a big round chamber and the metal ring on the shank. As to the discoloration, if there's calcification on it I've found that comes off with a good soak in some cola, and in my limited experience the cola doesn't discolor the mouthpiece (further) the way vinegar might. Some have suggested olive oil to reduce the oxidation, but that hasn't accomplished much in my experience. I wonder if a light polish might restore the black. Personally, I love old brown hard rubber - it highlights the quality of the rubber.