This is a Bob Reeves Classical Series 1 1/2C mouthpiece for cornet. I used it with my trumpet, matching the size. The instrument is a Martin Committee. (I felt a slightly heavier mouthpiece was preferable.) There are no markings, and the box is the only proof, but the throat size is 25. (There are no photos, but I'm including the box to prove the throat size.) *In short, this is a Bob Reeves-modified mouthpiece. It produces a rich, beautiful sound. Thank you for looking.