[Ron Ramirez]

what is the coil physically next to the Main Transformer, (bottom side)?

As I mentioned, that is the audio output transformer under the chassis. Smallish, mounted with two rivets. It will have three thick cloth-covered wires coming from it, another smaller wire, and a wire that you may not notice that is soldered to the frame. The smaller wire and the wire soldered to the frame are the leads for the secondary winding of the output transformer. The three thicker wires are the primary leads - one is a center tap.

Take a resistance measurement (with the set off and unplugged) between the plates of the 41 output tubes. If you do not have continuity, that transformer is bad (which is very common). This will not affect your set's power supply, but if bad, the radio will not play.