I am in the process of making 2 Besson euphoniums out of 3.
The background:
A friend of mine, Todd Clontz owns Rosso music. Todd is an excellent instrument repair man and many interesting instruments come into his shop.
A few years ago, he talked me into 2 Besson euphoniums. One is a fixed upright bell 3 valve compensating and the other is a removable bell-front 3+1, 4 valve compensating. The only problem was that there were missing parts: three valve buttons and 2 top valve caps were missing. So, there were only enough parts to have 1 in playing condition at any time. Todd had suggested we remove the fixed upright bell from the 3 valve and put it on the 4 valve. I played both horns and really wanted to have both playable. I would just switch the parts to the horn I wanted to play. However, the removable front bell was never really to my liking. It seems it was probably a concession to the American market to compete with the American style "euphonium".
Also interesting to note is that the front facing bell is larger in diameter that the upright bell (12" vs. 11"). However, according to the 1958 catalog, this was the same situation regardless of 3 valve or 4 valve. The ferrule where the bell joins the horn is the same diameter and the taper is the same up to the joint on the removable bell.
The donor:
Recently, I found and purchased off ebay another 3 valve compensating Besson. It had all of its parts plus plenty of dents. However, the bell, while wrinkled, appeared to be restorable. The bell came off easily and the major wrinkles were removed. Next step is to give it a really good rolling out on a dent machine.
The valve parts proved to be more problematic:
After sending them on a trip through the ultrasonic bath, I started to test fit the donor valve parts from the 3 valve onto the 4 valve. The finger buttons appeared to be the same as those on my other Bessons. However one had a different thread from the other 2 and would not thread into any other of the valve stems besides the one it came out of. The standard Besson buttons of that era are threaded 6-40. The oddball was metric! (M4-0.7) Even stranger was that the valve stem appeared to be original and not re-threaded or replaced. You may ask, why not just swap the valve stem? It is not that easy, Besson valve stems are soldered in to the valve top, not threaded.
So, we re-tapped the 4th valve stem to the metric thread and solved that problem.
The top valve caps were even stranger. 2 of the three were of slightly different inside diameter to match the slightly different valve bodies they came off of. The third was so large that it would not fully tighten on any of the 3 top valves on the 4 valve horn. Luckily, I only needed 2.
Below are pictures of the 2 horns before surgery plus a shot of the donor bell just after removal.
I will post more when the bell is smooth, polished and on the 4 valve.