I read about the NPL on the last page of Word Ways around 1969. It was just a brief description of the Enigma and an address. After I subscribed I was a little disconcerted to find I had joined an organization, but I was soon hooked. I had no contact with any other member until the first Princeton convention.
First issue: Feb 1971
My nom results from anagramming my last name, Kreger, into Greek R.