"weird XLR plug .... it's a lot biger than the regular one"
Maybe it's a Tuchel connector? The pins are flat, not round little rods. In that case, there's adaptors for that.. or somebody solders an XLR instead. Do a search for the correct pinout of the Tuchel.
How can i know if they are from 50's or 60's?"
Cast metal frame, these are old. Black plastic frame not. Gold colored cable, old. How's the serial number? About 50.000 were made back then.
"how much can worth those mics"
It depends. They are sometimes about 60 years old and even if they look good, not all of them still work like they were intended to. In Germany most people wouldn't give a toss, as there are many of them.. and they are old, very old and getting closer to the date where they go to microphone heaven. In the USA there are people so infatuated with the hype, legend and whatnot they pay silly prices. I have seen them go for 800$ and seriously doubt if they are worth that. 300-400$-ish would still be enough.
Word from the street says there's two places where we can expect clones in the near future and AKG isn't included. That would seriously drop the hyped prices.
If you got a good one and it works, just keep it and use it.
Property is not ability. Buying a drumset won't make you a drummer and buying gear won't make you an engineer.