Looks to be bolt-on. I think it might be an NS-94 from 1994-98. I found this archive listing on the Spector website. Pickup and dot inlays match and (although it's hard to tell), it looks to have the "longer upper horn" mentioned. No idea how those are rated as a bass though and what they were priced at when new.
(Edit: Scratch all that. NS-94 has a different, longer headstock). After a bit more digging, I'm leaning to it being a Q4 Pro - No idea how good they are/were and price etc.)