EARLY TUESDAY morning the nine presidentially appointed governors of the U.S. Postal Service are scheduled to convene around a large table in the Benjamin Franklin Room at the service's L'Enfant Plaza headquarters.

In what is expected to be a brief, closed meeting, the governors will decide whether to accept the recently proposed 29-cent rate for first-class letters. If, as many postal executives expect, the governors accept the rate, the first of many new rate-change stamps will begin appearing later that day at several Washington post offices.

By the end of the year, postal officials say perhaps as many as 20 new stamps will have been issued to meet the various bulk and discount rates that the Postal Rate Commission has said may become effective Feb. 3.

But on Tuesday afternoon, most of the attention will be focused on two of the new stamps, both preprinted without specific denominations and stored for months in an old salt mine near Kansas City, Mo., that serves as the service's national stamp vault.

They are the long-awaited "F stamp," a stamp bearing the letter "F" and the image of a red tulip, and a so-called "makeup" stamp that will sell for four cents and consist entirely of text. That stamp can be used to pay the difference between the current 25-cent stamp and the new first-class rate.

The "F stamp," which postal officials prefer to call "the flower stamp," is the sixth nondenominated stamp in a series that dates to 1977. That's when postal executives decided that since they could not count on the rate commission to approve the precise rates they requested, they needed a stamp that could be sold for whatever rate the commission approved.

Although the "F stamps" were ordered shortly after "E stamps" went on sale in 1988, officials have declined to make the designs public until Tuesday. The stamps, along with an F stamp for government mail, a government mail F rate envelope and an F stamp version of last year's plastic stamp, will be placed on sale at the main D.C. Post Office (900 Brentwood Ave. NE) and at the L'Enfant Plaza philatelic counter shortly after the governors meeting. The F stamp bearing the tulip and the makeup rate stamp should be available at most post offices Wednesday.

Individuals wanting a stamp imprinted with the 29-cent rate will have to wait until March 2, according to the Postal Service's stamp schedule. That is the day that commemoratives saluting the state of Vermont's bicentennial go on sale outside Vermont with the new first-class rate.

Designs for those stamps were revealed earlier this month in a ceremony in the State Capitol at Montpelier. Unlike the furor that was sparked by the 1989 North Dakota commemorative, the last stamp to carry the image of a rustic barn, Vermont's stamp has won the praise of that state's governor.

In one of her final acts, Gov. Madeleine M. Kunin declared that she was delighted with Vermont artist Sabra Field's design, a Vermont landscape with a red barn in the foreground and a mountain in the background.

"It's from her favorite artist," said Kunin spokesman Mike Wilson. "It's difficult to portray the Vermont landscape and the governor is absolutely thrilled with the design."

The stamp will go on sale March 1 in Bennington, the city where the Vermont legislature ratified the Constitution and made Vermont the 14th state.

Postal officials were hoping for a 30-cent first-class rate, but someone at L'Enfant Plaza seems to have had a hint of what the rate commission would decide. Two of the service's previously scheduled stamps for 1991 -- a new 4-cent stamp and a 50-cent commemorative -- will get extensive use under the decision. The former will be released Jan. 25, while the latter, which meets the new international airmail rate, will be released on Feb. 22.

"It's just a coincidence," said Postal Service spokesman Jim Murphy of the releases.

The 4-cent stamp, bearing the image of a steam carriage on display at the Smithsonian's Museum of American History, will go on sale in Tucson. Part of the service's transportation series, the stamp was ordered last year to replace the 4-cent stagecoach stamp that went on sale in 1982.

The first noncommemorative stamps bearing the 29-cent rate are not expected to go on sale until sometime in April. Two new flag stamps are to be released then. One will show the flag over the Mount Rushmore National Memorial and the other will show the flag and the five interlocking Olympic rings, a reminder that the service is a sponsor of the 1992 Olympic Games.

In what Murphy describes as another happy coincidence, the service had decided that its commemorative honoring the 700th anniversary of Switzerland would be priced at 50 cents. That stamp will meet the new international air mail rate, which will increase five cents on Feb. 3.

Redfaced over the new rates, officials at the United Nations Postal Administration canceled their plans for releasing a new 30-cent stamp and a new 50-cent stamp on Feb. 1. The U.N. had expected the domestic rate would be set at that level and were shocked by the rate decision.

A U.N. spokeswoman said that officials are attempting to revise their production to have some 29-cent stamps, but that it may be June before it will have any stamps bearing the rate.

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