TubeNet

I wonder if the seller meant Eb. It looks kinda similar to a Cerveny 641.

The Conn International line tubas were stencil horns. Wasn't it Cerveny that made them? Or someone else?

Thread from this spring Seattle CL: Conn International 87-J BBb 4 rotary valve. Wherein it was looking about the same, Eb Cerveny CEB 641 (or AEB 441, doesn't really make any difference as the Conn stencil isn't guaranteed to be either one.)