It's a Bohland & Fuchs BBb 6/4 tuba -- not really tall enough to be a proper Kaiser, but with a huge bore (.830"), very wide bottom bow and about a 21" bell. Marked "Imported for the Vega Company, made in Bohemia." Reminds me of a Cerveny 693 but with a horizontal tuning slide.
It is remarkably intact in all the valve tubing, BUT it is missing three rotors, all of the back plates and some of the stop arm mechanisms. Paddles and S links are all there, although one clockspring seems to have busted.
I do have one rotor and most of the parts needed for someone to machine up copies of the missing parts, except for the rotor backing plates.
![Image](https://i.imgur.com/VmW4CkW.jpg)