Raisa Gorbachev's letter to Nancy Reagan agreeing to a "summit" of their own next month in Geneva would command top dollar if collectors could only get their hands on it. Typed in Russian and signed by Raisa, it may well be the first letter ever written by the wife of a Soviet leader to the wife of an American president.

Currently in the keeping of James Rosebush, Mrs. Reagan's chief of staff, the one-page letter is destined for the Reagan Presidential Library whenever that becomes a reality. Meanwhile, its contents, read and reread by White House officials, should leave little doubt that Mikhail Gorbachev's wife, like Ronald Reagan's, is no ordinary pen pal.

Here's the text:

"Thank you for your letter of September 10. The thoughts expressed in it coincide with my own. The people of our countries, and indeed not only they, place great hope in the meeting between the President of the United States and the General Secretary of the Central Committee of the Communist Party of the Soviet Union. All expect that this meeting will serve the cause of peace and will justify the hopes of millions of people.

"Although our presence in Geneva is not officially a part of the negotiations, direct personal contacts are always useful. They facilitate mutual understanding. Therefore, I accept your suggestion to meet and spend some time together."

When the General Services Administration authorized the installation of new security doors leading to Secretary of State George Shultz's office this summer, nobody expected the project to be more than just that. In opening up the ceiling, however, workmen found asbestos, the fire-resistant construction material known to cause lung cancer and other respiratory problems.

The asbestos had to come out pronto, and since that meant partially demolishing the place, officials decided to go ahead months ahead of schedule with plans to build a three-room ceremonial suite, including an oval treaty-signing room, outside Shultz's office.

"We really didn't want to start work right now but it seemed the logical time," said State Department curator Clement E. Conger. Estimated to cost $1 million, the project will be paid for out of contributions earmarked for it by the State Department's Fine Arts Committee.

And what does treaty signing have to do with fine arts? Follow closely:

Treaties aren't signed all that often but agreements, accords and protocols are. The last time was in July when Chinese President Li Xiannian came to town. There were four back-to-back signing ceremonies, featuring Shultz, United States Information Agency Director Charles Z. Wick, Energy Secretary John S. Herrington and Edward E. Wolfe Jr. of the State Department Bureau of Oceans, International Environmental and Scientific Affairs.

Things got so jammed in the John Quincy Adams Room, in fact, that antique buffs in the crowd worried about what might happen to such priceless pieces as the Treaty of Paris desk. Said one State Department official, "Presumably, a treaty-signing room would eliminate that hazard."

What's a damsel to do with her compact when she's wearing her best slinky dress? She asks her beau to carry it, of course.

That's what singer Natalie Cole did at the White House dinner for Singapore's Prime Minister Lee Kuan Yew. The damsel-in-distress part came later when she wanted to touch up her lipstick and her beau was across the room.

Vice President Bush, seated next to Cole, gallantly went to the rescue by striding across the State Dining Room to where Cole's date, Metromedia's Karl Nurse, sat.

"You can imagine my surprise when I looked over my shoulder and heard the vice president of the United States asking for the compact," said Nurse.

In the Now-It-Can-Be-Told Department, credit CBS White House correspondent Gary Schuster for that close-up view of Xian terra-cotta warriors Chinese officials gave Naomi Nover of Nover News Service in the People's Republic last year.

"Knowing how much the Chinese respect age and power, I thought I might help her cause," said Schuster, president of the White House Correspondents' Association who was covering the Reagans' trip for The Detroit News at the time.

Nover, who uses an Instamatic for her photo coverage, wanted access to an area reserved only for professional photographers. Seeing her dilemma, Schuster, who does not speak Chinese, resorted to sign language. Over the unsuspecting Nover's shoulder, he pulled out an American dollar bill, folded it so George Washington's face was prominent and showed it to the Chinese official barring Nover's way.

"The official looked at Naomi, looked at George and never bothered her again," said Schuster. The White House press corps was agog watching Nover being assisted into the area.

Following last week's belated disclosure of the incident, Nover was enjoying new celebrity in the White House press room, where several colleagues asked for her autograph.

Said Nover: "I've never autographed a dollar bill before."

President Reagan -- who once said he wanted to take the "p" out of president and be a Washington resident like everybody else -- did what a lot of plain folks winding up a holiday did last night. He went out to dinner, this time at the home of his chief of protocol.

Solving her special protocol problem of how to decide who to invite from among official and personal friends, Selwa Roosevelt came down on the side of diplomacy: She and her husband, Archibald, asked only out-of-town friends to join them and the Reagans.

Among them were David Rockefeller and Willard Butcher, Chase Manhattan Bank's former and present chief executive officers, and their wives, Peggy Rockefeller and Carole Butcher, all from New York, and author Nick Gage and his wife, Joan Gage, from Boston.

Roosevelt gave Gage's book, "Eleni," the tragic story of the murder of Gage's mother by Greek communists, to Reagan for Christmas last year. At Camp David recently, the Reagans saw the movie version, starring John Malkovich as Nick Gage and Kate Nelligan in the title role. The film premieres in New York on Oct. 28.