1950's GE closed circuit monitor

[ChrisW6ATV]

Originally Posted by Olorin67

i was able to clean up the photo a little, here's the back panel.

Those are SO-239 jacks, whose matching plugs are PL-259s as already mentioned, together called "UHF" (utility, high frequency) connectors. It is common in the CCTV world for connectors to be in pairs for "looping" of signals from one device to another, but it is not clear if that is the function of the four total jacks on that panel. It also could be separate sync inputs plus a pair of jacks for the video.