Dish dude has the answers.
The TV is a hotel or institutional model. Move that part on the cord to the
"F" screw. The FM will work better now. The "EXT" jack was probably
for a pillow speaker. The knock out "ready plug" was to add an antenna
switcher, TV stereo or a Zenith based CATV descrambler.
Anything you add will go through the screw in connector ( VHF, UHF, CATV )
I think you will find the date of MFG is more like 1980.
73 Zeno
LFOD !