throughout the 60s, they stopped around 1970 or so
Those were designed to make it cheaper to sell low wattage MV as those times MV fixtures were very expensive and electric companies would not buy expensive low wattage MV to replace or use in residental lights, incandescent was still perfered over low wattage MV in the early 60s so General Electric, Westinghouse, PEMCO, even Line Materials and a few other companies have made a line of open bottom MV fixtures with less parts and metals to make them cheaper to sell. Even though they were cheaper, the ballasts was still HIGH QUALITY and WORK HORSES!
It's not a problem with the GE M-100.....but with the MO-8 it is only a problem if the cover below the socket falls out.....if it's not made sure it stays covered.
was this fixed? It looks like this is a 80s Fisher Pierce photocell. the window is missing. these had the windows glued on from the outisde so they fell off over time according Joe Maurath. so as long as the window stayed in place these would keep on going. The Ripleys on the other hand, it's the plastic that made them that ususally caused them to dayburn. The window typically got fogged up, not letting enough light in. Plus i think the relays weakened over the years with a lot of them. It's unfortunate since i really like them. The case gets tinted by the sun really badly too.
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I can see it has an older photocell, the current ones are black
Those were designed to make it cheaper to sell low wattage MV as those times MV fixtures were very expensive and electric companies would not buy expensive low wattage MV to replace or use in residental lights, incandescent was still perfered over low wattage MV in the early 60s so General Electric, Westinghouse, PEMCO, even Line Materials and a few other companies have made a line of open bottom MV fixtures with less parts and metals to make them cheaper to sell. Even though they were cheaper, the ballasts was still HIGH QUALITY and WORK HORSES!