ALL Form 109s are remote ballasted...they were GEs first fixture designed for MV. This was orginally designed for the old AH-1 medium pressure MV lamps 400 watt....ballast is electrically the same as modern 400 watt MVs
All clamshells are remote unless they have a HUGE cast metal body behind the refractor, then it has a ballast casing. Silver GE M-400 is the first to have internal ballast and is the newer verison of GE Form 109 while the Westinghouse OV-25 which was the first cobrahead EVER, and was the new version of OV-20
Anyways very nice light