Cruzing the alembic club is like a porn site cause there's soo many undressed naked B-asses to droul over......Its no wonder Bass players love to plug in!

Guitar players know more positions!  And we can sustain longer too! hehehehe
 
Bill, tgo

But Bass players love going down (low)........which makes guitars scream!

I'm hoping you can post a picture showing the electronics with the backplate off. Nothing in the file indicates this is anything other than a standard Series I bass. What was in the file:
 
top and back: Maple
body: Mahogany
neck: Maple and Purpleheart, 30.75 short scale
fingerboard: Ebony with mother of pearl ovals
peghead veneers: Walnut
birthday: April 24, 1978
originally made for: Rothchild, then sold to Thayer Music in Hawaii.  
 
One previous registered owner in Australia.
 
We sent a replacement neck pickup to the original owner in 1980 and serviced the preamp card at that time where we replaced two gain trimmers.  
 
In the correspondence with the original owner, there's no mention of the additional switches.  
 
So we're only a little closer to solving the mystery until I can get a peek at what's under the hood.