It's stunt trombone, it's a slide trumpet, it's the 314L!
This instrument is beautifully made and has a super sweet tone. It is very much in between in that most trumpet players haven't developed slide technique and most trombone players are accustomed to trumpet mouthpieces. Still, as an instrument to develop as a sight gag or a unique voice in your sound palette, it is satisying from even a critical perspective. It sounds really good and plays really well. It is a Bb instrument, and for a trumpet player who wants to develop some ability with the slide, or a trombone player who wants to pucker up a little tighter, it is a potentially expressive instrument.