A real head scratcher. If it has no effect of the light or movement thereof, why have a rheostat wired to the main toggle.
Maybe it was designed for deer poachers in states that didn't allow night hunting with an AR-15, and Mike's right; it controlled brightness so they wouldn't get caught.
Thanks Mike for clearing that up for me.
Mental picture of Mike's neighbours looking out their front window, wondering why Lynn is standing in front of the Airstream staring intently at the roof gesturing and shaking her head.