This is a Denis Wick 4AL euphonium/trombone large shank mouthpiece from the British instrument maker, "DENIS WICK," with a gold-plated inner rim. Rim Inner Diameter: 26.00mm Cup Depth: DEEP Throat Diameter: 7.34mm The mouthpiece offered here appears to be from a very early production run, judging by the engraving. The V-shaped cup provides a slightly darker tone, and it's easy to tongue. It also allows for good airflow. It has considerable age, so there are some scratches, but it's still perfectly usable! Feel free to ask any questions in the comments.