Some posters here (yeah, you know who you are )have wrongly identified various different models of streetlights.  For example, there is confusion between the General Electric M-400A1 Powr/Door and the M-400 split-door.  About the same time the M-250R was introduced, the M-400 was redesigned as practically a clone to the M-400A with notable exceptions.  The most obvious one being the rear door has no vent holes and a simple spring latch rather than a captive screw (early Powr/Door units had no vent holes, either, but had the captive screw). Construction features of the M-400 split-door include a taller PE receptacle, a longer upper "lip" on the top housing, and a housing-mounted ballast.

Another common one is the Westinghouse OV-25.  Some posters mistakenly date them as "1964" when the most obvious telltale features (PE receptacle position and lighter silver finish) give it away as a 1970s lume.  Remember, if the P-cell is in the middle, like on the original '57-64 version, then it is a true '64 OV-25.  IF the P-cell is moved back about 10" with the darker silver, then it's a mid-to-late 60's unit.  If the P-cell is all the way back, then it's a 1970's unit.

And yet another mistake is the Silverliner redesign of the 1979-1980 era.  All Westinghouse and Crouse-Hinds catalogs state that the models are OV-15 and OV-25.

I agree. I always go by the manufacturer designations of the different luminaires. The compact square Silverliners that came out in 1979, I call them "later style OV-15/OV-25s". You can tell a 1979 square OV-15 or OV-25 from 1980 and later ones, by not having a NEMA tag. Westinghouse was slow in adopting the NEMA tag system.

BTW, the first of the 1970s OV-25s had the dark silver finish. Then a bit later the brighter hammered silver appeared.

Were OV-15s still made in 1983?