If you own different Westinghouse (yeah Ripper444, I'm referring to you also) OV-25 luminaires from different eras take a close look at the refractor patterns in the glass. The original flat-bottom (1st generation) OV-25's pattern had straight striations along the sides. Whereas the 2nd generation OV-25 had three different refractor patterns as the Luminaire evolved. I believe the "transitional" lume (the one with the p-cell in the same position as the flat-bottom) used the same glass as the F-B. Not long after, Westinghouse likely went to the shallow glass refractor before going back to the familiar trapezoidial shape. This time, with the new logo just above a second circle. Now the glass pattern had straight striations that jutted upward. And finally, to the familiar zig-zag pattern that is still in use today on the Cooper lumes. Thoughts?
I couldn't really tell you which era of glass goes with which era of fixtures, but I will take some pics of mine soon and at least demonstrate some of the differences. My glass is all mixed with different fixtures, I probably have Cooper glass on old OV-25s. I've used parts from other lights to make working units.