This is a Smith-Watkins trumpet mouthpiece designed by British trumpeter Mike Lovatt. From their website (slightly edited).
The ML Studio is engineered specifically with todays demanding performance requirements in mind. The ML Signature mouthpieces offer exceptional qualities, incredible flexibility, plus impeccable intonation in all ranges.The mouthpieces are paired with a range of unique ML Boosters. These are available in 3 weights and screw under the mouthpiece rim creating a solid mouthpiece. With players demanding the perfect mouthpiece, Smith Watkins decided to collaborate with one of the UKs most in-demand professional players, and offer a select line-up of these mouthpieces. All ML Signature Series mouthpieces are produced on a precise, computer-controlled lathe to guarantee each one is an exact match to the one used by Mike. This is the ML4 Studio model. With an inner rim diameter of 0.634 it's only slightly smaller than a 7C. Cup depth is medium shallow, similar to the D cup. The M55 booster is the medium weight at 55 grams and is removable. Very full, dark sound with good overtones. Mouthpiece plays fine by itself, but really locks in and darkens with the booster. Although the description may say "used", this was on my desk at the Kanstul factory for a few years. Heck, I didn't know until recently that the booster could be unscrewed! Favorite us, and check back as we are listing more interesting and exclusive mouthpieces!
The item "Smith-Watkins ML4 Studio Trumpet Mouthpiece With M55 Booster" is in sale since Tuesday, March 23, 2021. This item is in the category "Musical Instruments & Gear\Brass\Parts\Mouthpieces". The seller is "trumpet_charles" and is located in Whittier, California. This item can be shipped worldwide.