Whilst it looks immensely cool and relic'd, it's really quite bizarre.
From what I can tell, it's copper plated aluminium - which (my science hat tells me) is a pretty bad combination: add a little electrolyte (sweat/sea water etc.) and POW! Galvanic corrosion.
Copper is eating the aluminium.
(and explains the battery-like residue)
I like science.
... but I'm open to other interpretation if I've got it completely wrong.
The bridge on mine started turning exactly the same way, and I wiped it down after every session. Very much like an old battery corroding.
And the headstock looks like a crown when you get some big old vintage chrome tuning keys in there.
Man, I miss that bass. It would be so hip and unique right now. And my wife doesn't understand why I've nearly stopped selling basses.

Thoughts on colour yet?