Special Envoy : Soviet Union: Ambassador Jack Matlock leaves Moscow after 4 1/2 years of high-profile diplomacy that has dazzled politicians and the public.

At the end, the American who lived in the big yellow house near the Church of the Savior on the Sands could no longer walk the streets of Moscow incognito with his wife, as he loves to do.

People, recognizing him, would approach and ask for an autograph or say something like, “Thank you for being here, for all you’ve done.” They might beg a favor, like helping their mother-in-law jump the queue at the emigration line.

For 4 1/2 years, the face of the United States of America here has been a balding, bespectacled man now in his early 60s, the son of North Carolina teachers. His often rumpled, style-unconscious suits would make many middle-echelon Kremlin apparatchiks (Communist Party officials) look like models from GQ.

Jack Foust Matlock Jr., “ambassador extraordinaire and plenipotentiary,” left Moscow on Sunday to close out a 35-year Foreign Service career. In many Soviets’ minds, there is no doubt that he has been the most successful U.S. envoy here in modern times.

“He was the right man in the right place at the right time, and this is a rare combination in today’s world,” says Stanislav N. Kondrashov, commentator for the government newspaper Izvestia.

Georgy A. Arbatov, director of the U.S.A.-Canada Institute, says of Matlock: “He now has astonishing popularity here--he knows people, and people know him.”

At noon one day last week, as movers carried cartons of his belongings to their van and out of Spaso House, the ambassador’s official residence, Matlock, tie-less and with the collar of his blue Oxford-cloth shirt open, sat in his study. He reflected about the change in U.S.-Soviet relations that he observed and had a part in bringing about.

No American has sat across the table from Soviet President Mikhail S. Gorbachev more often, or had more time to study him firsthand.

To the ever-recurring Western question, “Does Gorbachev mean what he says?” Matlock responds, “Yes. The fact is, I think he is at heart a democrat with a little d , in the sense that he wants to lead the country to an open society and one where sovereignty resides in the people.

“Some would say, ‘Well, he really doesn’t know where he is going.’ I don’t agree,” Matlock says. “He’s really sailing in uncharted seas in many ways. . . . If there is a reef coming up, then you steer around it.”

The two said their goodbys at the close of last month’s superpower summit.

Matlock, who served previously as ambassador to Czechoslovakia and as then-President Ronald Reagan’s special assistant for national security affairs, had one clear advantage over his predecessors--the Kremlin’s policy of glasnost , which no longer made things American automatically suspect.

He used it to the hilt.

Not only was he capable of speaking Russian fluently with his interlocutors--maybe the only U.S. ambassador who could do so--but he also broke from the Moscow diplomatic circuit and went into the heartland, where he delivered speeches or brief remarks in Ukrainian, Georgian, Kazakh, Chechen, Uzbek or Moldavian.

It was the diplomatic equivalent of the presidential hopeful who dons a 10-gallon hat in Dallas. His audiences responded with applause.

Increasingly often, Soviet television also carried Matlock into living rooms across the country. He was on the air again only last week, assuring Soviets that the Treasury Department’s plan to print a new counterfeit-proof $100 bill didn’t mean that the dollars they had scrimped to salt away were worthless.

The downside of all the visibility was that he became so recognizable that he reluctantly had to stop his weekend rambles on the Arbat, a shopping thoroughfare for pedestrians.

“I really think that we have been instrumental in turning around the opinion of a country subjected to propaganda for decades,” Matlock says proudly.

Under Matlock, Spaso House became something of an intellectual salon, the place for visiting American VIPs and Soviet movers and shakers to mingle.

These soirees had some unbuttoned moments: Dick Thornburgh, the attorney general of the United States who resigned Friday, stood after one buffet dinner to ask the befuddled Soviet minister of justice if he knew how to tell when a lawyer was lying. (“When his lips move,” Thornburgh said).

Matlock arrived on April 2, 1987, succeeding Arthur A. Hartman, who had spent a record five years as ambassador here. A greater contrast would be hard to imagine: Hartman was a suave, Harvard-educated New Yorker and a former ambassador to France. Matlock (BA from Duke, MA from Columbia), seems sometimes ill at ease in all but the most formal situations but can talk with great passion about Dostoevsky. His wife, Rebecca, is an avid amateur photographer. They have five children.

Matlock, who already had three tours of diplomatic duty in Moscow, took command of a post shellshocked by a sex-for-secrets scandal involving Marine security guards and the withdrawal by the Kremlin of the scores of Soviet drivers, interpreters and cooks who worked there.

“The first six months were tough professionally,” he says.

If there is a dark side to the story--and Matlock would dispute it--it is that during an era of unprecedented Soviet accessibility, the embassy here has been run as something of a nunnery, with severe restrictions on what diplomats can do and whom they can meet in their spare time.

Perestroika or not, Matlock says, experience shows this is the only prudent policy.

A key player on the Reagan team that concocted foreign policy toward what, for a while, was perceived by the White House to be an “evil empire,” Matlock dates the beginning of his conversion on Gorbachev to May, 1988, when he first saw the “theses”--proposed policy statements--to be discussed at a Communist Party conference.

“I read these, and said: ‘If they mean it--and it was still an if --then this is a new ball game,’ ” Matlock recalls. “Because for the first time, you saw in Communist Party documents words about the separation of powers, governments deriving their just powers from the people, the need to protect human rights--and as an absolute good, not just as some bone that you threw to a foreign country.”

Matlock, who was paid $125,100 annually, including a hardship bonus, leaves behind a grueling routine. (His workdays have averaged about 14 hours, he estimates, and he considered himself lucky if he could take Sunday off). He will be going to Columbia University for at least a year to write, supported by a grant. He plans two books, one on current Soviet events, which he will try to dash off in 60,000 or 70,000 words, and a second, more scholarly treatise, on how foreign policy was made during the Reagan presidency.

He will be succeeded by Robert S. Strauss, the millionaire Texas lawyer who is a crony of President Bush. The priorities for the next American ambassador, Matlock says, will be different.

“The next big task is to convince them (the Soviets) that they really do need to create a favorable investment climate,” he says. “This could be a tremendous investment opportunity, but they’ve got to get rid of their hang-ups, like their fear of always being ripped off.”