Hey - great instrument. I’m not convinced the bell end does anything! I think the hole down near the base is the tuning hole - it tunes the base note (since its hard to tune a bell ended instrument.
I’ve got one in the original tube and booklet that came with it. They were an instrument that kids in small towns could mail-order as a “band” instrument. Ever seen the music man? imagine a town without a budget and a bunch of kids playing these.
It looked to me like the “bell” is actually closed. In that case, the hole at the end has to be a tuning hole. Haven’t we also seen those wierd ‘ears’ alongside the window somewhere else?
Looks little like a Cooperman with a trumpet mute permanently attached to the end.