Hi Marcus,
I'm sorry that I haven't been able to get you this information sooner. But after 20 years, 1 month doesn't seem like too long

Believe me, I'd much rather do instrument requests than the annual taxes
Here's what I found in the file for your bass:
PSB-I Piccolo Short Scale Series I bass 78-1078
top and back: Coco Bolo
core: Mahogany
neck: Maple and Purpleheart, 30.75 short scale
fingerboard: Ebony with mother of pearl inlays
peghead veneers: Zebrawood
machine heads: Schaller
strings: Vinci (I'm sure they are long gone!)
originally made for: Rothchild Music Instruments, CA
birthday: April 27, 1978
The bass was returned to us in August of 1978 to repair a scratch on the back caused at a trade show and to file the fret ends down. Rothchild also asked us to replaced the preamp card and pickup selector switch which were damaged in shipping the bass back from the trade show.
There is no record of additional switches, or any ownership history. If you post a photo of the electronics cavity, I may be able to help you identify your mystery switches.