well, i can see that it's scotch-locked into the pickup wiring, so i could only speculate that it's a hall-effect devise for a msd effect, but if it is home made, and the guy decided to use scotch-locks, and cheap butt connectors insted of a better method, than any reliability just flew out the door. you could have seen a couple capacitors as part of the circitry, which can look like butt connectirs, or tiny batteries. mabey you can get a close-up, or just leave it off, untill you figure it out.