It is playable, not really leaky at all, (I've played a few outdoor - patriotic, etc. - gigs with it), and the plating is beginning to give up on the pistons.
These are terribly underrated (in my view), offer a default majestic type of sound (including when played by someone who might be a professional trombonist and - tuba-wise, a "doubler"), and I tend to personally like them better than those of a similar configuration which have followed.
Other than the piston material (un-plated stainless material) and the receiver size, I'm thinking these were pretty much the same into the early '70's.
I also have a complete (post-nickel plated piston era) Besson 3+1 valveset (NOT mounted on a tuba) sitting in a box (nice valve tolerances, no knuckle dents).
I also picked up (cheap/eBay) about the top 2/3rds of an OLD Yamaha YBB-201 17" bell, cut off even more of it, and fit it with a genuine Besson male collar.
Eventually this will become a nice (probably with a new finish) 3+1 compensating Besson with TWO bells, as 17" was the original UPRIGHT bell size, and Yamaha - early on - completely copied the Besson bell taper before Yamaha (as did Besson and others) added to the bell diameter.
The 3-valve compensating valveset has nickel slide tubing, so I'll probably use THOSE tubes on the final instrument, as those slide tubes - original with the 3+1 - are yellow brass.
I'm probably going to (though limited space, due to design) work out some way to make the main slide longer, as these instruments tended to be "sharp-natured". (I might - ?? - even find that I might have to attach 45-degree or tight 90-degree turns between the main slide bow and its legs, in order to make the main slide longer without it bumping against an interior lower bow, defining that it would also not be removable.
) Finally, I may work out a main slide thumb right-hand thumb lever/trigger system (on the back of the instrument) to kick out for E-flat in the staff (as this one pitch - in particular - is quite sharp, just as with a whole bunch of Besson B-flat compensating anythings-in-particular). This is not high on my list of personal projects, but (again) magnificent sound, only one really out-of-tune pitch, great everything-range, and I've got it stuck together well-enough to use it.
Everyone has seen pictures of these with the 24 inch recording bell in place, so here are pictures of it with the 17" (Yamaha, which is exactly like vintage Besson) bell in place.
oh yeah: I like the lower position of the mouthpipe (basically like the Yamaha YBB-201/321 mouthpipes) - which accommodates the detachable bell. Many people find the normal position of the old Besson mouthpipes to be something that tends to hit them in the forehead.
but (mostly) thanks to Besson/B&H of Edgware Rd.