NEW YORKER Braldt Bralds knows how to separate the trees from the forest.In Bralds' case, the results promise to be spectacular.

The Dutch-born artist was selected by the United Nations Postal Administration to design a set of stamps warning that the earth's forests rapidly are being destroyed.

The six stamps that the 37-year-old artist has created will give collectors a glimpse of both the threatened trees and the forests. The only catch is that collectors will need to buy three so-called miniature sheets of 12 stamps each to get the full impact of his design.

Despite the price, they won't be disappointed. What Bralds has done is create three spectacular mosaics that show three different forests: a tropical rain forest, a pine forest and a forest displaying brilliant fall foliage. Each design is printed on sheets of 12 stamps, laid out in two rows of six stamps.

Tear off a single stamp, and all you see is a tree or two, a portion of the threatened forest. Look at the full sheet, and you see an entire forest, the product of a design that allows each stamp to blend perfectly into the adjoining stamps.

"It bleeds like a wallpaper pattern," said Jill Kerns, an administrative officer at the U.N. Postal Administration. "It tricks your eye into believing it's 12 separate stamps, but it isn't," said Gisela Grunwald, the U.N.'s postal administrator.

It's an imaginative concept, and one U.N. officials said has never been tried, anywhere. U.N. officials said they devised the concept and Bralds, best known for painting magazine covers, won in a competition with more than two dozen artists. He was paid $12,000 for his work.

It took two years to design and print the stamps, somewhat longer than the U.N. had expected, but Grunwald expects that collectors will find the stamps worth the waiting.

The stamps are scheduled to be issued March 12 for use at U.N. facilities in New York, Geneva and Vienna.

If the printing by The House of Questa in London is anywhere as vivid as color brochures released by the U.N., Bralds may have found himself a new market. Indeed, the U.N. seems so happy with his work that each of the miniature sheets will carry the wording "Painting by Braldt Bralds" in the margin, a rare public acknowledgement for a U.N. stamp designer.

Although the stamps are being issued before the United States makes its expected rate change, the U.N. is printing the stamps to reflect the expected rate increase. The tropical rain forest stamps -- for the forest most endangered forest -- are being issued (for domestic and overseas letters posted from any U.N. facility) in 25-cent and 44-cent denominations.

The 25-cent stamps compose the upper half of the forest and carry the wording "Survival of the Forests, United Nations, 25c," in a light green border on the top of the stamp.

The 44-cent stamp carries the same wording in a dark green border that appears at the bottom of the stamp. That allows Bralds' design to flow without interruption across the center of the sheet.

The Geneva stamp, showing the pine forest, uses the same technique with a .50 Swiss franc and a 1.10 Swiss franc stamp; and the Vienna stamp, displaying the fall foliage, carries 4 and 5 shilling value. All the stamps may be purchased from the U.N. Postal Administration, United Nations, NY 10017, at face value.

Treasury Secretary James A. Baker III has announced the winning designs for the gold and silver commemorative coins that the U.S. Mint will begin producing in early May.

Under terms of the 1988 Olympic Coin Act, the Mint can sell up to one million gold coins with a $5 face value and 10 million silver coins with a $1 face value with any surcharge to go to the U.S. Olympic Committee.

The gold coins are supposed to weigh 8.359 grams, be .85 inches in diameter and be composed of 90 percent gold. The silver coin is to be 26.73 grams, 1.5 inches wide and contain 90 percent silver and 10 percent copper.

The Treasury paid nine artists $1,000 each to compete with the Mint's staff of sculptors for the designs and two of them will pick up an additional $2,000 each for submitting winning designs.

Elizabeth Jones of Philadelphia, the Mint's chief sculptor and engraver, produced a youthful Olympian wearing a victor's garland for the obverse (heads) of the gold $5 coin and Marcel Jovine of Closter, New Jersey, combined an Olympic flame and the interlocking Olympic rings for the reverse (tails).

The obverse of the $1 silver coin features an Olympic torch being passed with the wording "Olympiad XXIV." It was designed by Patricia Lewis Verani of Londonberry, New Hampshire, who created one of the winning designs on last year's Constitution coins.

The reverse, carrying the five interlocking Olympic rings, was designed by Sherl J. Winter, also a Mint sculptor in Philadelphia.

Sales and marketing plans for the coins, the only commemoratives the Mint will issue this year, will be announced later, a spokeswoman said.

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