Hi Duncan,
Here's the details I found about 78-1020:
Series I MSB-4
top and back: Peruvian Walnut
body: Mahoganny
neck: Maple and Purpleheart
fingerboard: Ebony with mother of pearl inlays
tuners: Schaller
peghead veneers: Vermilion
birthday: March 30, 1978
originally made for: private sale to an individual
There's a note that it was originally fitted with an LED dimmer control.