Well, one thing about this one to consider... it's evidently been back to Alembic for some work. You might give Mica a call on Monday to see if she can remember or confirm what is detailed in that letter there, but looking at the electronics cavity, it appears that the original 2-volume harness that bass would have come with has been replaced with the new pan preamp which is a very nice upgrade. It allows for a much better balance between the P and J pickups to be set, because each has its own gain trimpot. Other than that, it says "fix headstock". I'd ask for what. I can't see any evidence of a cracked headstock, so if Alembic fixed it they probably touched it up too.
It's a nice bass. I played mine on a gig last night, and ten years on it's still my go-to.