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. From some research, it seems as though Kleartone mouthpieces were relatively commonly included in various American stencil horns. The most common are the pieces made out of white plastic material that resembled Brilhart's tonalin mouthpieces. 

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