This was one of the most durable luminaires in the industry (I have three of them). 2nd generation with mismatched Holophane glass. This light was available with either Holophane or Corning glass refractors, depending on the year they were made.
Cool I believe I have both Corning and Holophane I think the Corning one goes to my 1957 flat botom. One has the W without the ball points and one has the W with ball points and a circle with cross hairs below it.
More durable than a M-400? I find that westinghouse lights always get stuck screws. The castings themselves have always been very durable though. I noticed GE cheaped out around 1970 or so with thinner castings. My M-400 split door and my two M-250R1s are much thinner (and lighter) and than my 1967 M-250A. The M-250A's top housing looks filed down on the bottom too whereas my 70s GEs are rough on the edges of the casting (top of the doors, bottom of the top housings).
Now my OV-10IB's cast piece is almost 1/4" thick. Talk about one durable (and heavy!) sonovagun! I guess back then they didn't really have the technology to make the castings thinner though which is why they were thicker.
I Think it may be more durable than the M-400 one time a tree limb fell on my 1957 flat bottom 25 and I was able to pound out the dent with a hammer now if you tried that with the M-400 it would probably crack the housing. I think it was that they just took pride in the workmanship back then.
Were the different refractor patterns used at specific times or was it just the case of whatever they could get their hands on first? btw, Was there a certain time that small GE lights used the deep glass versus the shallow glass? I tend to see M-250R1s and M-250As with both shallow and deep glasses and all were installed around the same time too. I personally prefer the deep glass on the M-250 lights though... Maybe with the exception of the 60s M-250R, which i think looks better with the shallow glass.
With Westinghouse/Cooper, it was a matter of WHEN they were made. The oldest refractor design with the big (W) logo was unique to the first generation flatbottoms. Same with General Electric
Now my OV-10IB's cast piece is almost 1/4" thick. Talk about one durable (and heavy!) sonovagun! I guess back then they didn't really have the technology to make the castings thinner though which is why they were thicker.