TubeNet

Check your email.

Looks like the bariphonium players on that record were M. Dee Stewart and Glenn Dodson.

M. Dee Stewart is playing a front piston valve American looking baritone.
Glenn Dodson is the one holding the rotor instrument.

Maybe someone knows what kind of rotor euph Mr. Dodson played on one of the trombone forums.

I remember seeing an old Conn catalog showing Dee Stewart as a factory artist.