I have recently acquired an old Martin 3-valve baritone/euphonium (take your pick, I guess). I'm planning on using this as a "project horn" with the idea of fixing it up and selling it -- and learning something in the process. Aside from the finish and the valves needing replating, it's actually in quite good shape (with a bunch of truly minor dings). I will almost certainly not get out of it what I will put into it, but it's an educational aid.
That said, it needs a mouthpiece. What it has with it is a Conn C3 that has seen better days. What I want is one that I can use effectively for testing it as I progress and that I also can pass on to whomever eventually buys it. (So I'm not looking for what I would regard as a good mouthpiece for ME for this instrument.) I would also like the mouthpiece to be as inexpensive as possible.
So ... Suggestions? A Kelly would be fine, for example (I quite like them myself), but what size? Let's assume that the buyer would probably be someone using it casually in a community band, or a student of some sort, or someone using it in a church group. Oh ... small shank. Which brings up another question: Would it benefit from replacing the receiver with a large shank receiver? Or would that just result in a mismatch to the horn?
This is an adventure (and an excellent excuse to buy some cool tools).