This is a Yamaha cornet mouthpiece. (From the Yamaha website below) ・Rim Inner Diameter (mm): 16.46 ・Throat Diameter (mm): 4.20 ・Features: Standard model for British-style cornets. Offers flexibility for technically varied performances. It's practically unused, having only been test-blown in a shop, but it has discolored due to poor storage. It might come off with baking soda and citric acid. It will be packaged and shipped via Yu-Packet Post Mini. Trumpet Cornet Mouthpiece