yeah, its an old-style plug for the flat-wire cable. can't get them anymore...
What I did was disconnect the antenna wire from the back of this plug, and connected it to a 300ohm-75ohm converter. (radio shack) This has 2 screws on it to which you attach the antenna wires (doesn't matter which wire goes to which screw), and a coaxial type plug to which you can connect a modern coaxial cable to your tv.
Someone posted a link here once to a catalog outfit that had the entire 12v
outlet/coaxial connector wall plate. If they don't make one that is set up to have antenna wire connected to the back of the plate, you can always use the converter I mentioned, and just hide it behind the wall.