Posted by Lew on February 21, 2002 at 15:51:19:
In Reply to: Conn questions.. posted by Steve Clark on February 21, 2002 at 15:05:48:
The opening is 7-1/4". The bells should be interchangeable between all 2XJ tubas. In other words, there is no difference between the 20J and 24J bells. I have a 1934 22J on which I sometimes use an upright bell from a 1967 21J, and it fits fine. The collar on a 20K sousaphone is also exactly the same size.
Your sousaphone serial number dates it from about 1925. I am not sure of the model number, but in the 1934 catalog that I have the only sousaphone listed with a 28" bell is the "Jumbo Sousaphone Grand," model 48K. It only came with 4 valves in 1934. They identify it as "similar to the 38K, but larger in bore and having an extra valve." Maybe they made this with only 3 valves earlier.