all had meaning. Area code, area. Exchange, neighborhood (or might also correlate with business versus home in an area). Even the number at the end could tell you, if you had some inside information or were willing to call a bunch of numbers at random asking for Jenny in Sales to map it out, whether it was part of a Centrex or standalone. @Reinhold {Rey} Aman: I find the exact opposite. At least in Connecticut, zip codes are spoken (2 digit) + (3 digit). After all, the first two digits tell which state you're in, and the last three digits are (as far as a typical citizen is concerned) random. Ken Meltsner said, I believe zip codes were originally set up to incorporate an older post code system -- (city name) + 2 digit code. Plowing through old books and letters, I've often seen addresses with "Cambridge 39? or "Chicago 05." The first one becomes 02139, the second 60605. I could see where this would encourage the pronunciation of zip codes as 3 + 2 digits; if you didn't live near a big city, you might go the other way, I suppose. [Vaguely related side note: 12345 is the zip code for GE's main plant in Schenectady.] Ken Meltsner said, MIT's Dormline, long gone, used a 1920s vintage rotary telephone switch, and numbers were assigned, in sequence, to each dorm and room. My dorm, for example, had 6 sections with the same room numbers in each, and no more than