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#3 is a switch and resistor. Which makes me think dash light dimmer, but that would be tied to headlights, not it's own switch. So maybe a intermittent windshield wiper controller? #1 & 2 make me think of a reverb spring, so maybe it's a audio gadget. I don't know how many cars had reverb units in them.So for nothing better, I'll go Reverb.
I'd have thought that road vibration would have really messed up the reverb effect, but i guess if you are parked it's OK.
Reverb did actually cross my mind from one of the pictures cuz it looked kind of like a reverb tank in there. I guess it was !But what threw me was, 1) the switch. Why such a big switch to turn on and off a reverb and 2) the TO-3 transistor.