[Ron Ramirez]

Hello and welcome!

Answers inline...

1) Are these the correct knobs for this set? The photos I have seen on radio attic and elsewhere show plastic knobs which match the escutcheon. These knobs are wood.

No, those are not the correct knobs. The correct knobs are plastic; the originals were Tenite as were the original escutcheons, and they, too, shrink, warp and disintegrate over time. Correct repros may be purchased from the same person who made the repro escutcheon for your set: Larry Bordonaro at Old-Time Replications.
http://www.antiqueradioknobs.com/partlistings.html

2) There are no label tabs for the push-buttons, not even Off-On or Television, and I don't see any way to put any tabs in. There is a single transparent plastic strip behind the tab windows which seals off the space. How to insert the tabs? Are they being reproduced or do I have to make them myself?

Unless you are lucky enough to purchase one of the original call letter tab kits sometimes sold on eBay, you will have to make your own. They aren't hard to do on any computer.

3) I have never seen this funky output circuit. It seems to be a push-pull output stage but with no phase inverter or interstage transformer. If I understand the schematic correctly they seem to be using the top output tube as a phase inverter, using the screen grid as a second plate, which they then couple to the grid of the bottom output tube. I would never have thought this would work but it sounds excellent. I notice that they use this circuit in the 8 and 9 tube consoles also, but the 10 tube consoles get a real phase inverter. Did I understand this circuit correctly?

Yes, you do. One of Philco's ways of pinching pennies, they came up with that idea for some of their 1937 models and used it a lot later on on sets such as yours.

4) The schematic (which also applies to the 41-255) shows separate indicator lamps for the different bands, switched by the band-switch. This set has only one lamp in that position, in a pivoting lampholder operated by a second dial cord driven by the band-switch shaft. The set-up is clearly original. Was this a running change or was the schematic always incorrect for this model? Both the schematic and the set indicate Code 121.

It was a running change, another way for them to pinch pennies - use one dial lamp as the band indicator instead of individual lamps for each band. The individual lamp idea works better - you don't have the problems of mechanical misalignment - but, of course, three bulbs cost more than one.