The Bartell Studio Guitar Amplifier was a tube amplifier using 2-6V6, 2-12AX7/7025, and a 6CA4.  Other than the 2-12″ speakers in a column configuration, it appears to be identical to the Natural Music Guild CA-15 amplifier.  This unit has had it’s original cabinet modified by the owner.

From Bartell employee Doug Donaghue:

“Yeah, I remember that one too.  Paul didn’t really ‘design’ the CA-10.  It was a slightly modified ‘rip-off’ of an amplifier that was originally designed (in the late 50’s) by (Bob Crooks over at Standel).  IIRC that one had a printed circuit board that all of the front panel controls mounted onto.  There was something else odd about it…  Oh yes….  Didn’t the ‘main’ printed circuit board and the front panel come as a single piece and they were ‘cracked’ along a line so that no hand wiring to the front panel controls was required?  I seem to remember that.  And it saved a bunch of time and hand assembly costs.  The down side was that it was just about impossible to replace a front panel control if it went bad.  The front panel and main circuit boards had to be removed together as one piece and it was damned near impossible to do that without breaking one (or more) of the electrical ‘traces’ on the circuit board where it had been ‘cracked’.”