On a black example like mine, the poles aren't black.
All the black bits you see are indeed wood, and there is no evidence anywhere of an earthing 'mechanism'.
Something that probably needs to be stressed is that these basses were not high-end, boutique instruments cooked up using only the finest ingredients. Far from it.
As built, they were novelty basses designed as something of a joke and absolutely built down to a price. All the electrics/electronics without exception were compete pants ... cheap, shoddy pickups connected to cheap, shoddy pots using cheap, shoddy wiring.
My bass is just glorious, precisely because I had a luthier strip out every electrical component and replace them with decent stuff. The core of the rebuild was this:
That's a Dark Star pickup which I was lucky enough to pick up cheap on eBay many years ago. Although the same width as the original (well, duh!) it's a fair bit 'deeper' so the slidy bit on which it's mounted had to be extended by nearly a centimetre.
For the avoidance of doubt, the sliding mechanism works really well as a tone control, with the upgraded electrics my bass sounds excellent, and it attracts attention everywhere I play it.