right: Boosey & Hawkes Sovereign (latter-1980's, fairly near the end of Edgware Rd. production)
left:
Made by B&S (shortly after reunification) machine parts (valves and slides) fit "fairly well", intonation is no-trigger-required (everything good, as long as the two lower G's are played third valve, and critical upper E-flats are played with 1-3). Some IDIOTIC things were done at the factory, which defined that it played far worse out-of-tune (and - I'm told - these idiotic things are "consistent"), but those were arithmetic (cylindrical tubing) problems, and not taper/complicated-logarithmic problems - thus fixable and - now - fixed. Sound is big, more tuba-like (compared to the Besson), and robust.
right:
parts fit, but pistons and inside-outside slide tubing fit is (using a nice term) "casual" or (more bluntly) loose. Sound is even and sweet - yet also (again: leaky, but NOT worn) a bit fuzzy, but (at least - with me behind it) not robust. Intonation is reminscent of the 1960's-1970's "Besson" euphoniums that I've played - requiring constant attention (ie. some pretty radical "lipping")...and yes, I know these instruments have their ardent fans and owners.
I'm thinking that - even though different colors - the size difference in the two bells (from the throat down to the bottom) is easily seen and easily seen to be stark.
suppositions:
...Admittedly, I've never played a B&S-made Besson "Sovereign" nor "Prestige" euphonium. Likely (surely?), the machine work (valves/slides) is more like the modern B&S/M-W/Courtois instruments (which are all made there)...so perhaps (??) the German Besson playing characteristics are sort-of-the-same, but (perhaps...??) stronger/more secure/less fuzzy-sounding than with these England-made instruments.
I own the Meinl-Weston stencil (and haven't owned it for very long). I formerly owned a Willson 2900 (yet with a large-shank receiver).
I'm not a euphonium soloist (at all), but use compensating (fully chromatic) euphoniums to play the 5th parts in written-for-bass-trombone brass quintets (Ewazen, Dahl, Sampson, et al), pick one up and - unapologetically - play out-of-character/judged-by-me-to-be-a-bit-risky high passages in otherwise-contrabass-tuba orchestral pieces (whereby the young composers/arrangers know no better, PLUS I don't care to play "let's see if bloke screws it up on the concert" games), and (lately - rather than being an "F tuba hero") I've been playing early 19th century ophicleide/serpent parts (labeled "tuba" in modern additions) with a euphonium...so I really LIKE my stencil Meinl-Weston (really large bell, and the really large bore - found on the largest bore euphoniums made these days) sort-of-more-tuba-ish-sounding euphonium (though sure: not quite) for that which I use it...
...but (when I find that I'm confronted with some QUITE high "tenor tuba" part - Pictures/Planets/Strauss/etc.) I also own an ancient metal-valve-guides (ugly-brown, with dark red ink painted-on name) Yamaha 321 - with the rarely-seen aftermarket dependent 5th rotor (as the receiver is smaller, the bell is smaller, and the bore is roughly 20/1000ths of an inch smaller and - again - I'm not a "euphonium hero").
