I've got these oddballs that i don't have a great idea exactly what they are......i've had one other piece like this in length...but it's got 2 odd bits....one is the extra long shank....my best guess is that might be for a Bb only piccolo to play in A.......has a really tight backbore.....other odd thing....and i have some very early trumpet pieces that also have this very thin rim .....maybe someone can give me an idea on these.......cup is similar to the B but a bit shallower...i can see how it works with the pivot system....it's not marked but it's unmistakably a costello...maybe his stamping was too big to fit on the shorter steps..