The antenna connector is what was universally known as a "burndept connector", used extensively on professional and some military gear [e.g. the British "Larkspur" series] for a couple of decades post-WWII.
There were right-angled and straight cable-plugs available, with a range of different-sized cable-entries to suit different coax-thicknesses.
See here:
https://harc.org.uk/?page=technical&sub=connectors and scroll down about half-way.
Now extinct on the new market; secondhand ones sometimes turn up at radio-rallies [look in the boxes-of-tangled-cables most sellers seem to have under their benches]