So I just bought another older horn which I wanted to use for my upper register work and becuase I heard they were very free blowing. SELMER PARIS DEPOSE 20 TRUMPET 1955 - Original Finish/Case/M.P. **GREAT PLAYER** | eBay This one is an old Selmer, I did a good amount of research on these. I'm come to the conclusion that this "Depose" model which means patened I beleive might be the "transitional version" between the older Grand Prix and the K-Modified Selmer trumpets. I originally thought this becuase of the lack of the "K-Modified" stamping on either the reciever or leadpipes on the K-Mods that I've seen online, no indication of "Grand Prix" on the bell and the bell engraving is different than the ones on the other two types. The reciever on this new horn just says "20" and no letter "B" after it. I've also read on the trumpet herald site somewhere that the Selmer "20B" which is a .456 bore is considered an "artist bore" being the choice for most trumpet players at the time rather than the Selmer 24B or the larger bore. Is it also true that the tubing wall on the 20B is thicker than the 24B? Can anyone confirm this? I'll get the horn within a week so I'll let you guys know what else I find.