EARLIER THIS month when American paratroopers came to Washington to celebrate their 50th anniversary, representatives of a New York stamp company greeted them with a set of colorful stamps commemorating the event.

There on the 75-cent stamp was an aerial view of two Lockheed C-130 airplanes discharging troops. On a $2.50 souvenir sheet the sky was full of open parachutes. Both that stamp and a $6 souvenir sheet, which showed a pair of paratroopers in battle dress, carried the logo of the U.S. Army Airborne's 50th anniversary reunion.

But these were not American stamps -- and, as the price indicates, they were not cheap.

Carrying a total face value of $9.25, they were the "tribute" of a grateful nation that had been invaded by American paratroopers and other U.S. military units seven years ago. The stamps were issued by Grenada, the Caribbean island best known to most Americans as the scene of a 1983 military action ordered by President Ronald Reagan.

Many stamp collectors, however, long have known the island as one of the world's most prolific stamp-issuing nations. Its release of the three paratrooper stamps was the latest example of an aggressive marketing campaign aimed at American collectors by its New York stamp agents.

Grenada last month attracted attention from sports stamp collectors by removing banned Cincinnati Reds great Pete Rose from a sheet of nine baseball stamps it had issued in 1988. The action, said to have been done at the request of Major League Baseball authorities, came as the sheet was being reprinted to allow five U.S. supermarket chains to offer the stamps in a promotional effort. Regardless of the reason, the change created yet another variety of Grenada stamps.

Attempting to tap new markets such as paratroopers, baseball fans and supermarket shoppers is an increasingly common ploy for Inter-Governmental Philatelic Corp. (IGPC), the ambitious and controversial Manhattan company that now represents the postal administrations of 40 countries.

Using mostly American artists, IGPC designs, produces and markets the countries' stamps to dealers and other promoters.

It is a commercial operation and IGPC spokesman Daniel Keren makes no apologies for the company's aggressiveness.

"We want to make as much money as possible," Keren said in an interview. "We work on a commission basis."

Keren does not deny that some collectors are offended by the zest of the company's efforts. But he argues that those collectors are "an anomaly. They are not the stamp market."

To IGPC, the market is composed of thousands of collectors who collect by topic, not by country. "There may be 10 to 20 times as many collectors who collect by topic" rather than country, he said.

If IGPC depended on people purchasing by country, it often couldn't sell "enough to pay the printing bill," Keren said. "Let's face it, for the smaller countries, there is not going to be anywhere near the collector interest."

But, he said, "There may be 20,000 or 30,000 collectors who collect mushrooms on stamps. And since we work on a commission basis, it would be foolish for us and work against the interest of our clients not to advise them of that."

So, most of IGPC's client countries, especially the cash-poor ones with little collector interest, opt for topical stamps -- and lots of them. Half of the company's clients have signed up for IGPC's popular series featuring Walt Disney cartoon characters. Railroads, ships, flora and fauna abound on other IGPC stamps.

That doesn't include themes and personalities rejected by the U.S. Postal Service. IGPC's Tom Roy said the paratroopers went to Grenada only after U.S. officials said no to their request for a stamp.

Consider Tanzania's recent set of 10 stamps featuring black entertainers, a set that is certain to appeal to the large number of philatelists who collect stamps featuring blacks and entertainers.

Created by IGPC, the East African republic's stamps saluted, among others, Eddie Murphy, Gladys Knight, Stevie Wonder, Bill Cosby and the late Sammy Davis Jr. That was enough to win the stamps extended coverage on MTV.

Roy, a former U.S. Postal Service public relations employee and a collector, said that the company is bringing new collectors to the hobby, something stamp collecting needs.

There's no dispute that by coming to Washington to offer the three Grenada stamps directly to members of the 82nd Airborne Division and other paratrooper units, IGPC was seeking out nontraditional collectors.

The company, which has most of its stamps printed in Europe, created special first-day covers for the American military units to sell and offered them the stamps at discounted prices in return for their cooperation. That's a sales tactic that the U.S. Postal Service is barred by law from doing.

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