This is one of the nicest old Bessons you'll find, with additional touches like gold tuning slides and valve caps. Seller's description is below the photos. I think I saw this a little while ago for a higher price (perhaps an offer for a lower price now would be accepted). Buy-it-now price is $2,500, and there is a make-offer button.
ITEM SOLD FOR $2,100 - GREAT BUY!
https://www.ebay.com/itm/Besson-Euphonium-Compensating-4-valve-Made-in-London-1970-Vintage/254295950295
Besson Euphonium Compensating 4 valve, Made in London, 1970 Vintage. Condition is Used. This horn is in amazing condition for it’s age! An added feature is the gold slides. This horn is a true gem of European craftsmanship from 1970. The horn includes a hard case, a Schulze 51 mouthpiece, 6 1/2 AL mouthpiece, and various instrument care supplies. There are not many left that are in this high quality condition. There are obvious points of wear that are visible in the pictures, but this wear is minimal when factoring in the age of the horn. The valves and slides are pristine. No red rot! The only real wear is to the outer body as pictured.