This is the first HELICON of that period that I've seen what appears to be a removale bell (sounds like you'll need it with a 23" bell!). A raincatcher sousaphone would also have this type of bell collar. More modern sousaphones make the 90 degree upward knuckle first.
Careful of that low pitch tuning slide when you put the horn on/take it off!
According to the serial number, it was made in the first 2 years of the relocation to Williamsport, PA, after Brua Keefer took over the company, but it was still called the "Henry Distin Mfg Co" then.
Looks like a formidable horn to me!

Instead of talking to your plants, if you yelled at them would they still grow, but only to be troubled and insecure?