I have seen these basses with model designation as the B40 (two plus two headstock), SB40 (ditto) and then the Force 40 EQ (Tele headstock).
The Vulture was a symmetrical design like the Scavenger bass or Wing guitars. The Vulture II - I am not sure, I have seen very early B40s referred to as Vulture IIs.
Rudy Sarzo played a black version of your bass in the Ozzy days- it was referred to as a B40. Old ads of this are available on EBay.
Early Washy basses (79-83) were in a constant state of flux, and I suspect that Washburn didn't really have a bass plan solidified until 82-83 when they were marketed as Force basses.
Attached, my neck-thru Force 40 EQ. Serial number 832776. $150.00. Awesome bass.
Two toggles and three knobs, one being a 'phaser/chorus' type effect.
Note the position of the pick-ups too- slightly different than your bass - more centered on the body.
It should be noted that by the end of the Force run ('86), these basses were referred to as a B40EQ.
A few examples of the 'flux' can be viewed in the examples posted here.
http://www.google.ca/imgres?imgurl=http ... CC4Q9QEwBA