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Hi folks,
I've just obtained a Conn "S" Mouthpiece, from the ribbed ring vintage, which I assume is 1930's.
Does anyone know which horn this mouthpiece was intended for? Smallish Eb Tuba? Standard Eb Tuba? Is this the same as the Conn "Standard" Mouthpiece?
Trying to find info about vintage Conn Mouthpieces is almost as hard as trying to find info on pre-model number Conn tubas. The Conn Loyalist lists the following for 20's and 30's tuba mouthpieces, but this one doesn't seem to fit into any of these categories.

JI-200 JI-400 Standard Eb Bass
JI-201 JI-401 Giant Eb Bass
JI-202 JI-402 Helleberg Bass
JI-203 JI-403 C.G. Conn Ltd. Special
JI-204 JI-404 Chief J. Kuhn
JI-205 JI-405 Geib

Does it resemble the current Helleberg 120S?

The only "S" and "L" Conn mouthpieces (although from a little earlier) that I've seen have been mellophone mouthpieces, "S" intended for F & Eb, and "L" intended for D & C.

They, however, can't be mistaken for trombone mouthpieces, let alone tuba mouthpieces of any key. Perhaps before going to the 1,2,3 & 4 designation, they just tried S & L, mimicking the mellophone sizing.

"S" may mean small shank. Try it in a standard BBb or CC tuba receiver and in a bass bone receiver, or if all else fails, measure the tip of the shank. If it's the standard .520 or thereabouts, it's a standard tuba mouthpiece. If it's .490 or thereabouts, or sinks all the way into a standard tuba receiver, then it's made for the older smaller Eb receivers.