If it were fretted, the serial would be stamped on the face of the fretboard, just below the 24th fret, as on most 1980s Alembics. You could also try the control cavity.
The number would be like 87 S 1234 so 2 digits for the year, letter S for a Spoiler, and the serial number itself, which would be roughly in the 5000 to 8000 range for the late 80s.
Why not upload some pictures?
