I think that dotted line is because the power switch is on that pot. Nevertheless, I’m not turning this on until I’m certain or have the correct capacitor. If I’m correct this pot would be the tone. I’ve noticed other old radios put the tone on the same knob as the power.
On the Marconi, no I wasn’t aware. I took basic electronics in the early 70’s in High School when tubes were still very much in use. I know the basics. Thanks for that information!