I pulled the neck pickup out and its labelled "67 neck" which makes me think it is/was a SJ5-67 Passive. Its got the normal hot (white) wire and ground wired up to the pot normally. But its also got a red wire hooked up to a battery. The base of the pickup is sealed.
Are you sure it isn't an 5-string version of the SD AJJ-2 lightin rod pickups??
They are fore sure out of production but that doesn't mean they don't exist.
It could as well be an vintage 5-string SD pickup with additional pre, ( I have no cleu why anyone would want that...). So is the sealing very professional (SD style) or a bit sloppy?