Help identify a MW tuba

[Twoconnguy]

So, like the idiot I can be at times (maybe onset of senility) I purchased a Meinl Weston Getzen from that certain auction site thinking it sure looks like an old 25. Now after starting the tear down for cleaning and straightening a few things I’m not sure what it is. Serial # is B-5174. Rotor casings are stamped 343, as well as the underside of the stop blocks. The bell diameter is just under 18” with no garland. The height is a little under 42”, hard to be accurate judging by bottom bow dents and previously rolled out bell wrinkles. The fourth valve slide is in the back and, slides are nickel silver. Any clues will be greatly appreciated.