[Arran]

The Philco manuals describe that funky output circuit as "Screen grid inversion" they do work slightly better for fidelity then a single ended tube but the power output is only marginally more, good enough for a table model in any case. If you look at the schematics for the similar sets with a phase inverter tube the power output is higher, some say the fidelity is better too, but I think that the B+ voltage is higher too.
Everyone is right about the knobs though, those wooden knobs belong with an older radio likely from the early to mid 1930s. The original style knobs were made out of a grainy coloured plastic like the escutcheon with a triangle molded on the face, Larry Bordanaro makes reproductions but his may have a set screw which the originals did not have.
Best Regards
Arran