Hi Toshiaki,
Here's the details I found in the file for this bass:
Spoiler SMB6
body: solid Zebrawood
neck: Maple and Purpleheart, 32 medium scale
fingerboard: Ebony with pearloid oval inlays
electronics: AE-1 (x2) wired in stereo (see more below)
originally made for: not recorded
birthday: May 15, 1986
This bass was at a pawn shop in Florida before. There's no details about owners or repair history.
I found this in the file:
Which shows how my dad wired the two AE-1 circuits to a stereo pickup selector. This is similar to an Anniversary circuit, though this was made 3 years before our 20th Anniversary.
The bass has only stereo output.
This is a very unique instrument.