The jp379B really isn't a 3/4 either and it is rotary. (ie. OLD-DAYS definition of 4/4, yet disguised - via compact design - as a 3/4)
Tuning characteristics are remarkably good, the rotor casing fit is superb, and the all nickel tubing slide alignment is as well. A couple of years ago they even added on a slide adjustable right hand thumb ring gadget which is pretty cool. Other upgrades (from a few years ago) include a nickel-brass mouthpipe and nickel-brass 4th-rotor-to-main-slide connector (see pic).
The Bell pancakes out to only about 15 inches, but the throat and the rest of the Bell along with the body are more like the size of a King or possibly (??) slightly smaller such as an old York/Holton overall size and taper.
The bore is pretty large even though the tuba is sort of small. It's just under .8" (being that this is a trademark bore of Cerveny, and it is a Cerveny copy).
It doesn't sound like a 3/4 tuba, and - truth be told - I don't have much use - in all the applications of my various types of engagements - for the sound of a typical 3/4 tuba. Experience tells me that - had Cerveny designed this model with a smaller bore - the sound would have ended up being more terse and less marketable. It's piggyish, but - in my view - much more useful... particularly being built in B-flat, and thus offering a usable "low F" with only four valves... As seen, there is ample room for an aftermarket fifth rotor.
It reminds me quite a bit of a long discontinued compact Meinl-Weston model called "Handy" (model 18), but I believe I like this Arion copy better than that old M-W model. ...It's probably pretty easy to tell that this is NOT a tall instrument:
long-discontinued Meinl-Weston "Handy" model 18
...certainly not the same, but similar:
The 379B (as well as my also-short-stature Holton) is also an ideal "covered orchestra pit" tuba (as so many legacy/restored vaudeville-era American theatrical stages have been enlarged in the past two or three decades - defining that a portion of their pits are now under the stage floor). I knew a bass trombone/tuba doubler who (again: decades ago) owned a M-W "Handy" 18, as they were mostly a Broadway-shows player.