Hi Oliver,
Here's the details about your Koa bass:
ser number: 79-1386
model number: SBI4
model name: Series I
top: Koa
body: Mahogany (darker than Koa)
back: Koa
neck: Maple and Purpleheart
neck feel: standard tending toward thin
scale: 30.75" short
fingerboard: Ebony, fretless with Maple lines
inlays: none
controls: Series I with Master Volume
side markers: LEDs
originally made for: custom order for Harbert's Music, WV
birthday: July 17, 1979