Thanks for the pics! Ah so it seems that the housing is identical just with no holes drilled in mine. I was thinking the PC socket area was different. Yeah I don't know where I'd get a 1-7/16" hole borer from. The biggest I have is an inch. The retaining screw holes seem easy enough to drill. Tapping them would be the hard part (and lining them up!) Locating the retaining ring will be a little challenge. I got a PC socket off a Westinghouse OV-400 that was all busted up but the screws were stuck so I broke the retaining ring apart to get the PC socket itself out (at the time I just wanted the PC socket since I was going to replace the chipped one on my RMA and would have reused the existing retaining ring, but since the chipped PC socket still functions fine I decided to leave it and use this PC socket in my OVX!)

No problem! You could use your 1 inch borer, or pick up a larger one,if you decide to try using your existing 1" borer, draw a 1 3/8" circle in the center of the blank PC area with a sharpie,then with a half-round file ream the hole out to the 1 3/8" circle as the aluminum is thin and soft. If you don't have a thread tap set then the easiest thing is to find a pair of #8 or #10 self tapping screws,drill the two holes slightly smaller than the screws and thread them into the housing. Unfortunate that the retaining screws were seized in the old Westy OV-400,it might have been possible to drill out the screw heads to rescue the ring.

Hmm, I wonder if you could make your own makeshift retaining ring with a large enough washer. Just carefully drill the two screw holes.

Thanks for the tips. Yeah the screws were really stuck in there. The ring was already brittle (I don't particularly like the plastic rings, the ones in the 60s used a large metal washer with a rubber grommet around it) so it snapped easily.

That is actually a Westinghouse designed P-cell receptacle.

Yes my Westinghouse lights have the same PC socket. The only difference is that the Westinghouse ones have slip-on spade connectors and the Cooper ones have integral leads.