Squareback vs round back alternator?

CLBER said
No specs visible on the coil, I have checked carefully.

Yes. Usually only the part number. Specs will be in your shop manual.
The most important part to find new old stock will be the distributor points and condensor.

CLBER said
It was #1889545 which turns into #2196316 and with that nr I could find it.

I can check that against new 1960s shop manuals.

Other end of repair positive wire should connect to ballast resistor. Where that is located, I don't know.