Michael Hartkopf used to have a site that laid out all of the taxonomy, but it seems to have disappeared from the Web. Too bad -- it was a great site. I think you are correct that the N suffix is for the older three pin DIN connector and the NC suffix for XLR. In any event, I don't think there is any audible difference. Of course cables for the N mics will likely be pricier.
I too have a couple of those mics - (NC) now that I've looked -- and they are indeed great mics for all kinds of applications.
To the OP, is the mark on the M201, just M201 with no suffix?
Edit:
OK, here's an authoritative posting by David Satz about mic suffixes: