It is a cool reflector. Is that the socket mount inside the reflector?

Yep, the socket is attached to the reflector (all the M-250As are like that).

Actually, both the M250A and the M400A sockets were mounted to the reflector.

Thought so but didn't know for sure. Was there any reason why the M-400 split door and M-400A didn't use the same style socket mount? It would make sense that they would, since they're the same light, just with different ballast locations. Yet the socket mount for the split door is entirely different.

The socket mount looks a lot like the B2255 socket mount. I guess another instance where Powerlite and GE have similar design features.

Yeah I swear they shared engineers or something lol. I wonder who copied who. The M-400A and M-250A came out sometime in 1966, the first year GE used gray paint instead of silver. The M-400 split door and M-250R1 didn't come out til 1970 AFAIK.

The M400 split door does not use the same upper housing as the M400A, so location of screw holes would be different.

The socket doesn't attach to the housing at all though. It's bolted to the reflector. Then the reflector/socket assembly is held in by two tabs on the socket assembly that go into the mounting bridge for the doors on one end and a screw that goes through the reflector in the middle. That part is the same for the M-400 and M-400A, so I wonder why they didn't just use the same socket bracket. The M-400 split door and M-250R1 had a more advanced socket bracket anyway. It also allowed adjustment of the height of the socket (could be put lower for further pole spacing or higher for lower glare).

I'm pretty sure GE came up with the designs first as the B2255 and the B2227 were only introduced in the early 70s. Back in 1966 Powerlite was still making the B2217/2215/2213 designs.

Ah yeah makes sense.I'm not that familiar with the Powerlite timeline so I wasn't as sure when it was introduced. I know the GE timeline best and have a rough idea on Westinghouse/Cooper and AE/ITT/Thomas & Betts.

Ahh here's my approximate timeline

1940-1966 Gumballs, 1960-1969 B2217/2215/2213, 1970-1992 B2255/B2227/R37 , 1992-2003 R47, 1997-2003? R7. The B2255 might have been made up to the late 90s. I'm also not sure when was the B2228 discontinued. My guess is since it was basically the 1kW variant of the B2255 (the only thing different was the socket mount), it was made the same time period as the B2255.

Ah I see. Thanks. I still want to rescue a couple of B2227/R37s from that defunct mental hospital but no progress so far.