With little fanfare, the postmark Americans have been accustomed to for more than a century is quickly going the way of the telegram and the rotary dial telephone.

Last month, the postal service finished deploying new equipment nationwide that replaces the traditional circle-and-bars postage cancellation with a computer-generated city, state, and date, slapped onto mail by a high-speed ink-jet printer.

“It’s far more efficient and it’s far less maintenance,” a postal service spokeswoman, Monica Suraci, said yesterday. The post office began phasing in the new cancellations at regional mail processing centers last August and completed installation on all 1,083 of its state-of-the-art canceling machines a few weeks ago, she said.

“It’s sad,” a retired engineer in Las Vegas who has been tracking the conversion, Bartley Billings, 80, said in an interview. “It’s very nostalgic to us old guys to see these old things disappear but, you know, that’s progress. As an engineer myself, I know technology moves along. You’ve got to face it,” said Mr. Billings, a past president of a group devoted to the collection of postmarks, the Machine Cancel Society.

With the demise of the traditional postmark, America is losing an icon ubiquitous in travel books, pop art, and historical memorabilia. This summer, for the first time, vacationers who send postcards home from trips across America will find their missives emblazoned not with the familiar circle indicating the geographic origin of the mail, but with two sterile lines of computer type.

Ms. Suraci said the postal service is pleased with the change to so-called sprayed-on cancels and thinks customers will be as well. “We have gotten very positive response on this. For the most part, it is probably going unnoticed,” she said.

While the reaction from the general public is hard to gauge at this stage, early response from the philatelic community has been decidedly negative. The latest issue of a weekly publication for hobbyists and dealers, Linn’s Stamp News, includes angry letters from readers who complain that the new machines often smear ink and obliterate stamps.

A collector from Flushing, Mich., Theresa Young, called the new dot-matrix cancellations “absolutely horrible” and griped that mailing dates are often illegible. “News about sprayed-on cancels should read more like a somber obituary instead of a gleeful birth announcement,” she wrote.

A curator at the Cooper-Hewitt National Design Museum, Ellen Lupton, said the computer-generated cancellations will not convey authenticity and verifiability the way the old postmarks did. “It’s the proof of when something happened. It’s very physical,” she said. “I think that sense of authenticity is what that stamped mark, the physically-made mark was all about.”

The traditional cancellation is to some extent a collateral casualty of the declining volume of personal letters, as Americans have turned increasingly to e-mail for person-to-person communication and to the Web for bill paying. According to postal service statistics, the number of individually-mailed, stamped First-Class Mail letters and cards has declined by 11 billion since 1998. Only about 18% of mail is now canceled by the postal service. The remainder uses metered postage, printed permit numbers, or cancellations applied by the sender.

The shifts in mail volume have encouraged the postal service to consolidate mail processing at about 180 regional centers, where the latest technology, like the ink-jet cancellation, can be quickly and efficiently deployed.

The current president of the Machine Cancel Society, William Barlow III, said cancellations started losing their significance years ago, when the postal service did away with the practice of canceling mail in the city where it was deposited. Now, most mail gives only vague hints of its origins, such as north suburban Virginia.

“That was the first step, the depersonalizing of cancels,” Mr. Barlow, a San Francisco accountant, said. He said that with the latest change and the haphazard printing the postmark is no longer a reliable indicator of much of anything.

“I think if you want to send postcards to people you better have pictures of the places on there because you’re not going to be able to identify them from the postmark,” Mr. Barlow said.

Ms. Suraci, the postal spokeswoman, said the traditional cancellation, while becoming more rare, will live on for some time because some mail is still canceled at smaller processing centers and individual post offices. People who want traditional cancellations can send their mail from those places, she said, although it can be difficult to determine where mail dropped in any particular box will be handled. Postal employees should hand cancel mail on request, she added.

In the long run, parents and grandparents may find themselves explaining to children just what that strange circle-and-lines symbol represents. “There are kids now that don’t know how to tell time on anything but a digital watch,” Mr. Barlow observed.

One upside to the change is that correspondence gathering dust in dresser drawers, nightstands, and shoeboxes could someday be collector’s items, if only for the postmarks.

“If it does disappear, then that would make whatever is in existence now all the more valuable,” the executive director of the Cardinal Spellman Philatelic Museum in Weston, Mass., Edward Sternick, said.