Rare, vintage Kleartone "Professional" Hard Rubber soprano mouthpiece.  I have NEVER seen one of these before, but they are definitely designed for a vintage horn since they are a very short shank, large chamber soprano mouthpiece.  No facing markings, but in very good condition with only one small nick in the tip that doesn't go through to the chamber so there is no problem with reed seal.

No cap or ligature included, but it does come with it's original box.