IN THE OLD societies of Europe, it has long been common (if that's the right word) for members of the aristocracy to have as surnames those of their ancestral lands, preceded by the coveted "von" or "of" or whatever. We suspect that one reason hereditary aristocracy has never caught on in this country is the natural reluctance of people to say, "Greetings, I am Clarence of Silver Spring" or "Pleased to make your acquaintance; we are Sherri, fourth viscountess of Falls Church."

There is an alternative, however, and that is simply to slip into your next introduction to someone the five digits of your Zip Code. For those numbers, far more than the names of places, are coming to be the indicators of status in America.

We were reminded of this the other day by an item in The Post concerning a magazine on architecture. In its early days, the magazine was distributed free to certain Zip Code areas in Manhattan that met its high standards for income, education and other socioeconomic indicators. Then it expanded to similarly blessed Zips in other parts of the country. Now it is also being distributed to people outside those precincts, but they must pay $80 for nine issues, and even so will probably be ashamed to put their Zip Codes on their letters to the editor.

A Zip may not have the same ring as the name of some estate, abbey or geographical feature, and it is admittedly not encrusted with the history of the average duchy. But demographically, it's far more reliable than any of these, and is worth a small fiefdom to the mail-order merchant seeking the sort of households that will pay $45 a pound for a shipment of smoked salmon. Those five Zip numbers speak to him more eloquently than any ancient place name does of quiet streets, old trees, fine manses, coming-out parties and contented herds of expensive European automobiles.

So should the postman ring at your door, hand you a free publication on architecture, and say, "Your magazine, my liege," then you will know you've arrived. Henceforth, you may count yourself a member of the aristocracy of Zip, entitled to be announced at soirees as "lord of certain lands possibly exceeding one-fourth of an acre and of residential properties under chattel mortgage within the postal domain of 20093 -- the honorable Mr. or Ms. Occupant."