[Jeffhs]

It looks to me as if that set has a hi-fi audio system as well. I saw a separate chassis to the right of the TV chassis, connected to the main chassis by several cables which looked an awful lot like an amplifier, or perhaps it was the power supply. (On second glance, I saw several large electrolytic capacitors on that chassis; the line cord looks like it is attached there too). The speaker looks like it's at least 8" round.

I also saw a switch on the antenna terminal board, just above the antenna terminals. Does this have anything to do with the tuner, or was it connected in some way with the chassis in the right half of the cabinet, looking at the back of the set?

The split-chassis design is unusual, to say the least. If this set is/was an RCA clone, it is unusual, as I don't remember ever seeing stand-alone RCA color TVs with split chassis. Philco had at least one split-chassis set in the '50s (my best friend's parents had one, a 21-inch console with two side-by-side chassis [power and deflection/IF-video/audio, IIRC] connected by a multi-conductor cable), but ita's set is the first RCA lookalike I've seen with this design.