What is this Voltage Regulator

Several brands sold them, and Ma had one look-alike and maybe WAS the same they called and MP part. There is a huge controversy, "race only" etc etc, and the bit about "constant output" or whatever is EXACTLY what a VR is supposed to do. Only caveat with those is make SURE the case is GROUNDED. (I see the paint has been scraped off. Both Blue streak and NAPA sold them at one time. They "should" be a good regulator