I'm 99% certain that horn used to be mine. I traded it for a Besson 4v comp BBb. That helicon is the same size/spec as a 14K sousaphone and is, hands down, the most responsive marching-style tuba I've ever played. For the record, a 20K-style neck was included when we swapped horns.
Some more info about this horn:
-Serial dated it to 1902
-Engraved ornately on the bell with "C.G.Conn Elkhart & New York"
-Two top third valve slides, which made for easy intonation adjustments on the 1+3 C and the 1+2+3 B
-It's a comfortable horn. I never weighed it, but there's no way it weighs more than 25 pounds. It's balanced VERY well.
Whoever decides to get it will not be disappointed.