It's almost sounding like they took an engineer who designed some of the 7" electrostats and said "hey, wanna work on a big one?"
Me thinks this set was very much designed to a price point. The only thing that concerns me is the added cap on the v. linearity. I'm reasonably sure I traced out the disconnected caps correctly by the schematic. There's quite a few sloppy solder joints in this set, but I've cleaned them up and traced them out and they appear to be right.
There's even a factory 4 section filter can where only 3 sections of it were used. The 4th is just empty. I've only seen that on really cheap off brands. They must have sold these sets at Woolworth's or something
As I started to do the filter caps, I moved over one of the corroded resistors and a big chunk of the ceramic flaked off. Time to place a Mouser order.