During the “convertible craze”, everyone was trying to offer one of those for sale, and B&H rigged up their 2-20 Besson (aka 7XX B&H) to market in that manner.
From a certain number of years (I’m thinking: from the late 70s into the mid 80s), it seems as though most of them sold were set up that way. The nicest thing about them is that they were sold in Winter cases, which were darn good cases.
Seems like you could fit a normal leadpipe to that and have a serviceable tuba. Probably cost just about as much to have that done as it would to buy the tuba.
They were originally sold with two mouthpipes, just as with all the other convertibles.
That NEMC New Jersey company flooded the market with them (Which is why so many are seen on eBay Which is why so many are seen on eBay, today). No one around here cared about the marching mouthpipe. They ended up being lost, and the concert mouthpipes kept coming loose. Most of them around here: I soldered the concert mouthpipes on to those instruments “solid“, because the stupid oddball screws to attach the mouthpipes to the receivers were difficult to get from Besson.