It would be interesting to see the "back view" of that horn, but I bet it is not much different from the last bend of a Sousaphone (before the bell ring) rotated 180° and the bell inverted - if it was made with two mounting rings it could be reverted to a standard Sousaphone shape in a few seconds!
Somebody with a semi-assembled Sousaphone (not me at this moment) could check my theory pretty quickly. I just tried doing it in Photoshop but that didn't work too well.
I used Google's new patent drawing search to find a "rear view" of this thing - pretty much as I guessed - two screw rings to allow reconfiguration (to a standard-ish Sousaphone shape) and storage.