I get involved in this discussion regarding weight: the euphoniums you weigh are around 9/10 pounds. My personal Prestige 2052 is 11,13 pounds (5,05 Kg) with lighter caps and without mouthpiece, water collector and trigger protection. If you add these things and LeFreque plates do 12,32 pounds (5,59 Kg). I'd be curious to know if it's just my particular instrument ( German made, 2007), or other Besson Prestige owners have the same weight on the specimens in their possession( Besson indicates 4,7 Kg ( 10,36 pounds), the weight of the Prestige).
2007 Besson Prestige 2052, 3D+ K&G mouthpiece; JP373 baritone, 4B modified K&G mouthpiece; Bach 42GO trombone, T4C K&G mouthpiece; 1973 Besson New Standard 3 compensated valves, 3D+ K&G modified mouthpiece; Wessex French C tuba, 3D+ K&G modified mouthpiece.