TO THE NATION'S stamp collectors, it's already beginning to look a lot like Christmas.

That's not just because the country's annual pair of Christmas stamps go on sale this coming Thursday in ceremonies in Evergreen, Colo., and Washington.

Most collectors know that the holidays are fast approaching because this is the time of year that the Postal Service hurriedly issues its final batch of new stamps for the year, hoping to get the hundreds of thousands of envelopes bearing first-day cancellations out of the mail system well before the crush of holiday mail begins.

This year's final burst of new issues began this past Thursday morning in Washington with the release of a 50-cent picture postal card saluting Constitutional Hall and Memorial Continental Hall, two historic buildings near the White House that are owned by the Daughters of the American Revolution.

The new stamps that most Americans want -- the nation's Christmas stamps -- will be going on sale in separate 11 a.m. ceremonies Thursday morning in the National Gallery of Art's East Building and at the Hiwane Homestead Museum in Evergreen, a Denver suburb.

In what has become an annual fall ceremony that attracts hundreds of collectors to Washington, the nation's "traditional" Christmas stamp will be dedicated alongside the original art on which the stamp is based.

This year's stamp, the 15th Madonna taken from the works in the National Gallery, is based on Sicilian painter Antonello da Messina's Madonna and Child, painted in 1475. The original is a tempera and oil on wood; the stamp was engraved so carefully by Thomas Hipschen of the Bureau of Engraving and Printing that the wooden background seems clear.

The "contemporary" Christmas stamp, the companion holiday stamp which is devoid of religious symbolism, also has a tie to Washington. It was designed by Libby Thiel of Byran's Road, a Maryland suburb, and probably matches the Postal Service's mandate for bright and colorful stamps as well as any Christmas stamp issued since the series began in 1962.

Thiel's stamp features the outline of a white, cut paper Christmas tree, decorated with green garlands, red balls and yellow and blue swatches of color, all set against a fire truck red background. It is being issued in Evergreen because the town's postmark will help reinforce the stamp's image on first-day cancellations, according to Jim Murphy, a postal spokesman.

The designs of the two stamps follow well-established formats, with the traditional stamp bearing the lettering "Christmas" above the Madonna's image and the wording "Antonello, National Gallery" underneath. The contemporary, which is being printed by the gravure process, carries the word "Greetings" under the tree. Both have the required "25 USA" denomination in white lettering in a corner of the design.

As with last year's Christmas stamps, the Bureau of Engraving is printing all copies of the traditional stamp, using a combination of intaglio and gravure printing, as well as booklets of the contemporary stamp. American Bank Note Co. is printing sheets of the contemporary stamp.

What's surprising about the DAR card, part of a long-running historic preservation series, is that it comes in the format of a picture postal card. The Postal Service introduced its first picture cards last December and, despite the attention the first two Washington scenes received from collectors, the service has had difficulty selling them to tourists. The cards are designed to sell for 50 cents each, more than three times the price of the 15-cent cards available at all post offices. Retailers have been offered deep discounts to sell the first two cards, but the effort has not met with much success.INDIVIDUALS

wishing to secure first-day cancellations of the Constitution Hall post cards should send an addressed return label for each card ordered along with 50 cents to: Constitution Hall Postal Card, Postmaster, 900 Brentwood Rd. NE, Washington, DC 20066-9992. All requests must be postmarked by Nov. 10.

Collectors may prepare their own envelopes for the Christmas stamps with stamps purchased at their local post office after Oct. 19 or request postal workers to affix the stamps on up to 50 envelopes at the stamp's face value. Collectors who purchase their stamps should mail their envelopes to: Customer-Affixed Envelopes, Traditional Christmas Stamps, Washington, DC 20066-9991 for the traditional stamp or Customer-Affixed Envelopes, Contemporary Christmas Stamps, Postmaster, 3649 Highway 74, Evergreen, CO 80439-9991 for the contemporary stamp. Requests for postal workers to affix the stamps should be sent to the postmasters in the respective cities and all requests should be postmarked by Nov. 17.

Bill McAllister is a member of The Washington Post national staff.