YOU DON'T have to be a stamp collector to like the Olympics, but it helps.

Stamps that celebrate the games have become one of the most popular of the topics pursued by collectors and this winter's games in Calgary promise to create yet another bumper crop of sports stamps.

Olympic stamps have become so popular that E. J. Smith, who runs a Crofton, Md. stamp firm that specializes in "topicals," says many countries have now started issuing them in three phases: a pre- Olympic series promoting the upcoming event, a second series for the actual games and then a post-Olympic series promoting the local teams that won.

Canada, as host of the 1988 Winter games, already has begun issuing a series of stamps to promote the games February 13 to 28. A pair of 36-cent green and red commemoratives featuring cross-country skiing and ski jumping went on sale last Friday.

Four more stamps marking the opening of the games will be issued February 12, at the opening of a stamp show called Olympex 88, which will be held in Calgary during the games. These stamps will feature curling, alpine skiing, figure skating and luge. The first two in that series will be issued in 36-cent denominations for domestic mail, one 42-center for mail to the United States and the luge stamp in a 72-cent denomination.

The United States plans a single commemorative next year to mark the games, and it reportedly will feature an alpine skier. It will debut about the same time as the games begin.

Canada is on a sports kick. Its final stamp of the year is a 36-cent commemorative marking the 75th playing of the Grey Cup, the trophy that goes to the winner of that country's professional football superbowl. The multi-color stamp, to be issued at the game in Vancouver, Sunday, November 29, features a football zooming across a field on which the trophy has been superimposed. The lettering is similar to that used on sports jerseys.

And the just-announced 1988 Canadian program will include a 36-cent commemorative to mark the 150th year of playing baseball in Canada on September 9.

Stamp dealer Smith, who runs a mail-order business under the name of Crofton Philatelic Co., said that collectors who follow the Olympics are among the biggest group of collectors that his firm services. "I would have to say that I sell more soccer stamps than any sport," he said.

He'll probably get his chance to add a lot of soccer stamps later in 1988 when countries begin gearing up for the 1988 Summer games in Seoul.

"The Koreans already have begun contacting dealers about the stamps they'll be offering," Smith said.

The Bureau of the Mint, which produces the nation's coins, has a collection of coins and medals that foreign nations have given the mint's director over the years. But visitors to the Mint headquarters on Third Street are allowed to see only one side of a French medallion honoring Marilyn Monroe.

If you want to see the reverse, a nude Monroe, stop by the visitors center at the International Monetary Fund for an exhibit of French coins and medals through December 31. The exhibit is open from 10 to 6 weekdays.

The Postal Service has found another use for the colorful flag with fireworks stamp it issued earlier this year and, in the process, may have found a way to ease the shortage of stamp booklets at Post Offices across the country.

Faced with an annual shortage of about 40 million stamp booklets, the service has convinced the Bureau of Engraving and Printing to take stamps produced on its conventional presses and then trim the sheets to booklet size. Previously booklet stamps have been produced by a special press, but it has been unable to keep up with the growing demand for booklets, officials say.

The new booklets to be issued here November 30 will include 20 of the Flag with Fireworks stamps that were first issued in sheet form May 9. Stamps from the booklets will be easy to identify because they will lack perforations on at least one side.

Collectors desiring first-day covers may send envelopes with stamps attached to Customer- Affixed Envelopes, Flag with Fireworks Booklet Stamps, Postmaster, Washington DC 20066-9991. The Postal Service will affix one stamp at a price of 22 cents each for envelope sent to: Flag with Fireworks Booklet Stamps, Postmaster, Washington DC 20066-9992. The deadline is December 30.

Bill McAllister is a member of The Post's national staff.