In early FIDE ratings files what does a flag value of "n" indicate? Here are examples from the January 2002 FIDE ratings file -

   4603745  Kabisch, Thilo                         GER     2256   12   06.01.63 i    
  13701940  Kabov, Sergey                          KAZ     2140    0   28.06.67      
    931900  Kacarevic, Dejan                       YUG     2068    0   13.10.79 n    
   4136497  Kachanov, Alexander                    RUS     2091    0   02.07.59 n    
   4140729  Kachar, Vladimir                       RUS     2363    0   19.01.41 n    
  13600613  Kacheishvili, Giorgi             g     GEO     2584   25   10.02.77      
   4623614  Kachiani-G., Ketino (IM)         wg    GER     2460   17   11.09.71 w    
   4138996  Kachkin, Konstantin                    RUS     2134    0   21.04.78 n    
   4167678  Kachkina, Ekaterina                    RUS     2079    0   03.11.86 wn   


The flags value is the last field. The value "i" indicates that the player is inactive, "w" that the player is female.

Interesting to note that Kachiani-G., Ketino has "(IM)" after her name as well as titles field "wg". Presumably this is meant to show that she was both an International Master and a Woman Grand Master.
Going through the January 2002 list, I notice that these "n" marks seem to concentrate on certain countries.  Everyone from Russia, Yugoslavia,  Cuba, and Latvia seem to have this "n" mark.

If you look at the April 2002 list, you'll notice that now everyone from the Philippines also has an "n".  Perhaps the "n" stands for "nation" and designates something about the player's country.