IT WAS HARDLY a secret. They began printing the stamps three years ago, and since "E" follows "D," everyone knew what the stamp would be called.

Finally, some would say, the Postal Service has made public the design for the long-awaited E stamps. They are the stamps that have been lying in postal vaults around the country, waiting for the Postal Service to make official its next rate increase.

The increase is expected to go into effect later this spring. While officials long have assumed that the new first-class rate will be 25 cents, they took no chances when the E stamp was designed three years ago without a specific cent value.

What's interesting about the stamps is that they mark a radical departure from the one-color art-deco eagle that adorned the A, B, C and D stamps that have been used since 1977 to introduce new rates.

The E stamp features a view of the Earth taken from outer space -- a view that is based on a painting that the Postal Service said was based in turn on National Aeronautics and Space Administration photographs. Designed by Robert T. McCall of Paradise Valley, Arizona, the stamp shows a burnt-orange North America under a veil of swirling clouds.

There's one caveat to the Earth stamp. It can't be used to send letters around the world. Like all the previous letter stamps, it's good only for domestic mail.

The Universal Postal Union requires that stamps on international mail carry a specific denomination. The stamp carries the word "Domestic" to warn users of the limitation.

The Postal Service also is planning to issue an Official Government Mail stamp without a denomination and an official government envelope as well. There won't be such a postal card, however.

The E stamp will be sold in sheets of 100, booklets of 20 and coils of 100, 500 and 3,000 stamps. The issue date for the stamps will be announced later.

If you have some A,B,C or D stamps lying around your house, rest easy. They are still valid for postage -- if you can remember what they are worth. Here's some help:

The orange As were issued in 1977 for the increase to 15 cents from 13 for first-class mail; the purple Bs were released in 1980 for 18 cents each; the reddish brown Cs for 20 cents in 1981; and the green Ds for 22 cents in 1985. Actually they're all worth more than their face value to collectors, with the D stamp topping the list at 44 cents each in unused condition.

If you're planning to put them on a letter, remember your letter must have enough postage to meet the current rates. If you don't have any letter stamps, don't worry. Given the budget troubles in the federal government, it's a good bet that no sooner will the Es hit the streets than the Postal Service will begin printing some Fs.

There is another bargain at some Post Offices. Postal officials have acknowledged that some customers who have purchased new booklets of the 22-cent U.S. Flag with Fireworks stamps have gotten quite a bonus.

It seems that, instead of one sheet of 20 stamps, a number of the booklets have slipped out of the Bureau of Engraving and Printing with two sheets, or 40 stamps. "We don't know how extensive it is," said Hugh McGonigle of the Stamps Division. "The number reported seems to have fallen after the initial flurry."

Demand for stamp booklets is booming and the Postal Service has been pressuring the Bureau of Engraving, part of the Treasury Department, to buy more of the presses needed to produce booklets. The Flag with Fireworks booklet, introduced last year, was produced with stamps printed on the Bureau's conventional presses.

Troubled by the prospect of giving away stamps, the Postal Service has taken two steps. It has urged all its sales personnel to double-check booklets before they sell them, and it has urged the Bureau to add extra personnel to check the booklets before they leave the 14th Street plant.

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