I prefer the M-400A FCO over the M-400A2 FCO but i still like this one. It's almost the same thing except this has a bail latch and no top housing grooves.
There were actually two versions of the M400A1 FCO. The earlier version had the lamp socket attached to the reflector and disengaged power when the door was open. You then rotated the socket assembly to relamp. This is why the socket was street side mounted. These also had stippled glass lenses. The later versions with the clear lenses were more traditional house side mounted lamps.
This one has since been replaced by a LED. All the traffic light safety lights, over 400 of them in the city, got replaced. But this particular light has been saved It's 1989 vintage. Another M-400A2 from this intersection was also saved, that one still got the original GE LU250 lamp with the old etch.
Interesting lantern. How does it look from below? Can one see the lamp in it?