Just out of curiosity:

From time to time I see Besson large bores that have the Yamaha-style F attachment closed wrap that also many of the Chinese instruments (and I think Jupiter at some point) use.

Any clue if there is a background? Besson buying valve sections from Yamaha or from China at some point?

I don’t think Yamaha sells valve section out, or at least not with price low enough for other manufacturer to make profit. I would lean toward Chinese-made.