The horn here may be from the 1960's according to the seller, but it has a large mouthpiece receiver. Perhaps it was swapped out at some point. It's in very good shape, including the pistons, from what I can see. Starting bid is $750 and the BUY IT NOW PRICE IS $1,500. This should go quickly!
THE HORN SOLD ALREADY (NO SURPRISE) - CONGRATS TO THE WINNER!
https://www.ebay.com/itm/BESSON-New-Standard-Euphonium-silver-compensating/224047829983