Interesting. It looks like an early (batwing headstock) SB900, with some unspecified mods. No such thing as an SR900, btw.
The original SB900 was passive, seller claims this is active so maybe has had circuitry installed. Not 100% sure about controls for an early 900 (they were changed later) but I think this should be v/v/t, 3-way rotary selector, plus coil switch for each pickup. So no idea what's going on here! The bridge pickup's a replacement - it is an Aria unit but not correct for this bass.
Anyway this is what it should look like:
Intact examples of early SBs aren't very common but I'm inclined to think this is a bit overpriced for a bass with a number of unspecified mods. Putting it back to stock would be borderline impossible - while (costly) repro pickups are available, the knobs used on these simply don't exist anywhere other than on other basses - I've been looking for a pair for an SB-Elite for four years!
With this one, I'd want a very close hands-on look at it, and the seller would have to be prepared to be haggled at, hard!