I got this used 55-01 as a gift and I love the way it plays, however the electronics in it have me confused to all hell. I get the feeling someone modified the wiring in this bass. Here are some photos of the bass and wiring The pearloid knob is obviously the master volume. It is the only knob that isn't notched. The four black nobs all are notched at their midpoint. The black knob closest to the bridge seems to be a pickup blend knob but I'm not sure. The second one increases the volume when turned clockwise and decreases counterclockwise. The third black knob from the bridge can be pulled up (as pictured). When pulled up, it gets really loud when I turn it up and pretty soft when turned down. When it's in the lower position, it does the same thing but it's not quite as hot. I have no clue what the fourth black knob from the bridge does. According to the Lakland schematic it's supposed to be the master volume but it obviously isn't. I've done my research and can't figure out how the electronics in this bass are set up. The pickups are bartolini mk-1 split coil and it has a bartolini pre-amp (mk-1 I think). I would really appreciate some help from someone who knows more about this than I. More pictures are available if you need em.