After some research I found out the wiring, tested it with an EMG 85, and it worked great. Haz Labs could also confirm that it is from a Steinberger guitar, so I guess the pickup also is from the same guitar.
In one of my many boxes from years ago with guitar parts I found this preamp. After some research it is maybe from a Steinberger guitar, and made by Haz Labs. The wiring is not complete, does anyone know anything about this, or how it is wired?