This is a mouthpiece for a long cornet. It's a vintage mouthpiece, the details of which are unknown, but it's a deadstock item that has been stored unused for many years. There is some clouding due to aging, but I think it can be cleaned up with polishing. The cup shapes are compared in the sixth photo. From left to right: YAMAHA 11C4, Denis Wick 2C, and Jettone DS. It's shallower than the YAMAHA, and I think it's about the same as the Denis Wick 2C.