[Ron Ramirez]

Then, I too am leaning towards undocumented Phactory Phranken-Philco.

I can sort of see a cable dangling from the upper chassis with a four-pin connector which mates with the four-pin chassis plug on the back of the SW converter chassis. This connector provides B+ and filament voltages, as I mentioned earlier. But that 51 would still have to have a beefed-up power transformer to be able to run the 51 chassis and the SW converter chassis.