WHEN AMERICAN and Soviet officials gather in Baltimore this fall to dedicate sets of similiar stamps being issued by their countries, they will be paying tribute to an 12-year-old proposal by one of Washington's premier stamp designers.

It was 1978 when Peter Cocci, a banknote engraver at the Bureau of Engraving and Printing, first came up with the idea of issuing stamps to call attention to some of the world's endangered sea creatures. His first proposal called for a single 13-cent commemorative that would feature a blue whale.

Cocci, who has designed some of the nation's most popular stamps, had heard that the U.S. Postal Service was interested in producing more stamps with "topical" designs, especially ones featuring mammals. So, with the encouragement of postal officials, he did some research of his own and came up with another proposal, this one for a block of stamps that would feature four endangered sea mammals found in waters around the United States.

The Citizens' Stamp Advisory Committee, the group that reviews stamp proposals, liked his idea, and asked Cocci for several revisions of his drawings that would fit into a booklet format. The idea remained under active consideration but lacked a specific release date until last year's World Stamp Expo '89.

That's when Soviet and U.S. postal officials met in Washington to release sets of similiar, but not identical, stamps showing future methods of space travel. That release led to discussions about another joint release similiar to the pair of stamps they issued in l975 to celebrate the joint Apollo-Soyuz space mission.

Last winter they settled on Cocci's proposal for four sea creature stamps. Under the agreement, the United States was to design two of the stamps to be released Oct. 3, while the Soviets did the other two. The U.S. would prepare the drawings for printing at the bureau's computerized design center in Washington.

In a ceremony at the National Aquarium in Baltimore last week, the designs for all the Soviet and American stamps were revealed and they appear to be a tribute to Cocci's ideas. Although the American is credited with designing only the dolphin and the killer whale stamps, Soviet artist Vladimir Beilin appears to have drawn heavily on Cocci's concept for his views of a northern sea lion and a sea otter, the other two animals in the block.

While all four animals are set against the same blue sea background that Cocci had initially proposed, the foregrounds are different. One of his early proposals called for using the humpback whale, sea walrus, dophin, and manatee, but the subjects were revised to include animals that would be common to both U.S. and Soviet territorial waters.

Cocci said last week that while his art may have influenced the design, the Soviets had a major impact on the format of the stamps, the same size as last year's dinosaur stamps. The U.S. Postal Service also agreed to the Soviet custom of placing the year of issue on the stamps, but it stopped short of agreeing to place the stamp designer's name on the margin of the stamp sheets. That means sheets of Soviet stamps will carry Cocci's and Beilin's names, but the margins of the U.S. stamps will note that two were "prepared by a United States designer" and two "by a Soviet designer."

Like the 1975 joint Soviet-U.S. stamp issue, the primary differences in the stamps will be the languages and the printing processes. The U.S. stamps will be printed by the bureau using a combination of offset and intaglio processes, but the Soviet stamps will be produced entirely through an offset lithography process by Goznak, the State Security Printing House.

Although the type used for the lettering is identical, the intaglio printing should make the lettering on the U.S. stamps more distinctive. The American stamps will carry the first-class rate of 25 cents and the Soviet stamps will be valued at 25 kopecks (42 cents), the cost of mailing a registered international air mail letter from the Soviet Union.

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