"Come back after awhile. It will be more interesting," he promises. The Secretary of the Treasury looks different.On two earlier occasions, he looked cocky, self-assured, a jubilant ham, alternately feigning outrage and modesty.

Now he looks sad and vulnerable, his expressive face down and pale, the ever-present cigar between his fingers, long dead.He is, for the first time, in his shirtsleeves. He is, as usual, in muted colors, unremarkable clothes bisected by a gray, thin tie.

"I refuse to be called a wearer of skinny ties." With an effort he rallies, examining his tie with unbounded admiration. "This - this is a brandnew Dunhill. I bought it at a very 'in' men's shop. As a matter of fact, I can't afford to buy this tie any more."

He has said too much. From time to time, he beats the side of his fist against the arm of his chair. The week before he had announced that his wife, Eileen, and he were separating after almost 26 years, three children. Now he would rather talk about anything other than that.

He won't even talk about her as she once was - when for instance, W. Michael Blumenthal got her to marry him by sending out wedding invitations to all their friends.

"I don't feel at his point I want to get into anything about my wife," he says. "It's not a good time to talk about personal things." He looks up, his entire face a plea, "You understand that, don't you?"

He is asked where he is going to live now - a house or an apartment?

"I don't know. Got any suggestions?" Then he shakes his head decisively. "No, not a house. It would be much too lonely in a house. I don't want that."

"What's that on your wall?" An economics reporter points to a framed newspaper clipping hanging in Blumenthal's office at the Treasury.

The new Secretary curls his bottom lip in amusement. "Oh that. That's from a Berlin tabloid." He obliges by translating from the Berlin dialect that is the headline: "A BERLINDER IS TO BECOME CARTER'S NEW MINISTER OF FINANCE."

He does not read from the other part, which adds HE HAS THREE DAUGHTERS AND A TENNIS COURT." Instead he says, his tone determined stripped of all sarcasm, "I thought since they kicked me out of there many years ago, that was sort of a nice thing to say. We had sort of come full circle."

As indeed they have. Werner Michael Blumenthal was born 51 years ago in the Germany that put his father in a concentration camp, which is undoubtedly why he now says, "I've been back to Germany many times. I've never felt any part of me was there.

But since he and his family left it when he was 13 - after buying the father's way out of the camps - there is, of course, still something of Germany with him. The accent for instance - milder than Kissinger's (as he makes sure to point out), but there for all that. The reticence and the discipline.

And finally, because the flight of the Blumenthals brought home to the ghettos of Shanghai, a city that was bombed by a steady battery of Allied B-29's during World War II there's a resilience to Blumenthal, a fierce survivor's instinct, somewhat masked, somewhat mellowed by age - not to say a toughness. He, for instance, does not say toughness.

"Toughness" he echoes, "Well, I'm not a very good judge of that. You newspaper people - you feed on yourselves. Yes, you go to your morgue (library) and you read all your clippings on me, and you say, 'Blumenthal - he must have been a tough boy.'"

He shakes his head, smiling ironically. "Yes. At 16, I left school, and like a lot of other people in a wartime situation, I worked to keep body and soul together. But I don't know if that makes you a tough kid.

"If you refer to the fact that Shanghai was for all young people a rather liberal education, that is true."

"It was" - he drawls out the word - "an experience. You know the expression Shanghai-ed? Yes, will it was a den of iniquity. There was opium dens, gambling, prostitution, adventurous gangsters. And assorted folk congregated there, and you saw a lot of people from Central Europe pulled out of their own environment into a totally foreign situation.

"And a lot didn't make it."

And those who did, in fact, make it, have these memories of Shanghai they carry with them to this day. Blumenthal's old friend, Isaiah Zimmerman, for instance, who is now a psychiatrist in Washington, says that as teen-agers, they both cleaned the corpses off the streets of Shanghai.

"He was very traumatized in Shanghai," says Zimmerman, who knew Blumenthal well only when they came to this country. "And of course when we cleaned up the dead bodies off the streets - it was such a horrible thing. The smell of it was horrible. (The experience) probably made him feel he had to rely on himself.

"In the ghetto, nobody was really looking out for other people . . . When the bombs came, we would go to the cellar every night.

"Yes, you'd always leave a few things downstairs, to make yourself cozy . . ."

But Blumenthal avoids most of the details. He talks of Shanghai only when pressed. Blumenthal says, "You know there was a person in Shanghai - a person who had been an editor-in-chief of a major newspaper in Germany. I can't remember his name now, but he was transformed into this new setting (of Shanghai).

"And that person totally went to pot in Shanghai. He wouldn't wash, and that was an important thing, you know, with only cold water. The only thing he did was eat.

"An yet there was another fellow who was my friends in Shanghai. He had left Germany alone at the age of 17, had quit school at 14, from the German lower class. And so he came alone to a place like Shanghai, at 17. And he make it. He fought as a professional boxer, worked as a waiter, and survived as a human being with dignity and worth.

"From that point of view," he concludes, deeply earnest, "that environment - though tough - was a very good school for a young person."

He cocks his head thoughtfully for a silent moment. When he finally speaks, he said, "I did learn that you own inner resources are what make you.

"I used to ask myself - I still ask myself - you know, when I meet someone with a pedigree and a big desk and an important title: How would YOU make it if you were shorn of your desk, your background, and your language?" Goodbye to Germany

He arrived in this country before his parents, at the age of 21, the determination now, not merely to survive, but to triumph - an important distinction, and one which seems to have dominated his life in this country.

"I never think in terms of 'making it.'" he insists. Then immediately goes on to add. "When I got to this country, my goal was to get into a college. And that was my ticket to The Millenium."

The smile mocks its owner. "But then I realized - to go to San Francisco Junior College - well, I couldn't get very far with that.

"So then I decided to go to Berkeley, I thought -" he raises a hand, fingers splayed, "THAT'S the ticket to The Millenium! Then I thought - No. All A's, a Phi Beta Kappa, THAT'S the ticket to The Millenium.

"So all right. So I get all A's. So I did get into Phi Beta Kappa. And then - WOW - I thought I'd get into one of those really well-known graduate schools. Like Princeton."

And so - wow - he did get into Princeton, where in five years he earned three degrees: an MA, a masters in public affairs, and a doctorate in international economics. By then he had married Margaret Eileen Polley, a lady who has her PhD in education, who made a career for herself, teaching. Princeton asked him to stay on as a professor. "I felt then that I had succeeded," is how Blumenthal put it to another interviewer. 'Making It'

"But "making it," he says now. "I've never really felt that way. I tended to have particular goals as I went along and each goal is succeeded by another one."

All through school he worked. "I was always looking for jobs in order to make money," he recalls. "In between my junior and senior year, I went to Lake Taboe, and I began to work as a busboy.

"But I soon discovered that a busboy in California makes much less money than if he were where the money is [Nevada]. Where the dollars are rolling."

That last idiom sounds quite extraordinary, delivered, as it is by a clipped German accent. Blumenthal knows it; the smile grows broader still, as he says, "So I decided I had to clean up.A friend of mine who is now a shrink in town here - we went up there and got jobs. We decided to maximize our income."

Here is how Isaiah Zimmerman and Michael Blumenthal managed to maximize their income where the dollars were rolling. They became in one summer: busboys, laundry truck drivers, lighting assistants and - finally - gambling shills. "Each of us would sleep once every two days," reports Dr. Zimmerman. "We became quite proficient at lighting the shows at the Calvada Lodge.

"The comedian would introduce us as the two professors from Berkeley and Princeton who were roughing it. And we did the lighting for Nat King Cole and Lily St. Cyr - who did a reverse strip. And we'd sit in the kitchen and talk about life with the Mills Brothers.

"Mike was always kind of unflappable," says Zimmerman. "He was so stable. He never went to pieces . . . He was very tough, and at the same time he was very gentle and considerate.

"And he always had a feeling for the ridiculous." Multimillionaire

"Did you know that So-and-So is richer than you are?" an adviser to Blumenthal needled him recently.

The Secretary looked momentarily perturbed. "How did you know that?" he demanded.Then he shrugged it off with, "Yes. But it took him 20 years to make his money. I did it in six."

Blumenthal maintains that it isn't money that interests him. That it's an accident that be became a multimillionaire.

"Well it IS an accident, as a matter of fact," he replies to the chuckle. "What's a multimillionaire, anyway? To me it's someone with many millions."

So how many millions does he have?

He shakes his head, only mildy amused. "I don't discuss that. It's gross. But if I had been interested in money, I would have spent my time amassing it. I would not be sitting here." His arms embrace his office. Blumenthal leans forward, head lowered as if to butt the point home.

In fact his attitude toward wealth is best summed up by an old friend of his from Bendix Corp, his former employer, who says. "Mike is not interested in money as such. For him it is a key to freedom, a measure. It is a mechanism, an instrument - and from that point of view, he's very much interested in it."

But Blumenthal prefers in discuss money in terms of his career. "After Princeton, I went to Crown Cork International. But when I left that, I took a cut in pay to work for the government."

He began that stint in 1961, as deputy assistant secretary of State for economic affairs. Then, in 1963, he was appointed to head the U.S. Delegation to the Kennedy Round tariff agreements in Geneva. It was there he achieved quite a reputation: as tough, as brusque, as very shrewd.

Joe Laitin, Blumenthal's public affairs man, recalls an incident when a conference with Carter kept his boss 40 minutes late from an appointment with reporters. When the Secretary was at last able to see them, Laitin was delayed by a phone call, and the reporters arrived late.

"You are," Blumenthal told them as he consulted his watch, "Five minutes late. We shall have to cut this short."

"I think that's why he's such a good negotiator," laughs Laitin. "He knows how to keep people on the defensive."

Laitin, as it happens, is sitting in on this interview, listening as his boss says, "The key to my personality - and I shouldn't be doing this for you - but the key is, when you see what I've done, it's been negotiating."

And yet, the Secretary is told, he does not look somehow like a very patient man . . . .

Blumenthal throws his hands up in the air. "Well, that's because you read all these things about me. Your mind is contaminated." He turns on Laitin. "I'm a person with little patience? I challenge you."

"No. I don't think so," Laitin soothes. "But you are also a harsh task master."

The Secretary doesn't look entirely thrilled with that. "I do have patience. I have a lot of patience. I am capable of losing my patience, and I am not the most patient of men. But that's all I say."

Laitin says, "You do suffer fools. But not gladly."

"Yes," says Blumenthal, mollified, "I have learned to keep my mouth shut and smile benignly."

He smiles benignly. A Man With Class

Bendix, a multinational corporation that makes car equipment, space equipment, wanted Blumenthal because he had international experience, negotiating experience. Bendix wanted Blumenthal because he had, in a word, class.

Blumenthal wanted Bendix because, he says. "The Bendix people were really nice.So I picked that company even though it wasn't the best, the highest offer I could have picked."

And Bendix wanted Blumenthal because for some time it had done - to quote Blumenthal - "Rather badly." Swiftly he corrects himself. "Indifferently. Until '64. In '64 there was a new chief executive.

"And that man set out to reorganize the company and bring in new people. And he did a lot. I became president in '70."

And he became chairman in '72. "And chairmen," he explains genially, "are very well compensated because of stock options. And then I had money."

Then, in fact, he had quite a bit of money. In the 16 months before he went to the Treasury, he got, it was reported, $2 million from Bendix, part of which was earned in previous years - which took the form of salary, bonuses, consulting fees (future consulting fees - for after he leaves office) and stocks - a considerable portion of which he'll have to dispose of by Oct. 31.

"Which is very nice." He leans back in his chair. "I'd hate to say I hate the idea. But just as I was at really top earning power - I quit."

He lets that sink in. "I took a job that pays one-eighth to one-tenth of what I earned before. I certainly didn't come here to maximize my income. So when I'm 65 - so I won't have $10 million. So what? What am I going to do with it? Leave it to my children?"

He shrugs expressively. Question From Carter

This is the way he got his present job. First he was a Mondale man. Then a Jackson supporter. Then he lent his name to the Carter candidacy. And then . . . here it comes . . . Jimmy Carter called him down to an economics meeting at the Pond House ("It is called the Pond House - isn't it?" Blumenthal asks).

After the election there was a second Pond House meeting.

"Would you be prepared to help me out?" Carter asked Blumenthal, who figured maybe he was in line for a No. 2 or 3 cabinet post, and therefore replied, "Well that would be difficult."

"Impossible?" asked the President elect.

"No. The problems are not insurmountable."

Twenty-four hours later Blumenthal got a call at Bendix.

"You said the problems aren't insurmountable," Carter reminded him. What problems."

Well, said Blumenthal, I have no real desire to leave my job. I have responsibilities, shareholders. I wouldn't want to leave all that unless you have a really important assignemtn for me."

"I do," he was told.

"Oh," said Blumenthal. "Well, if it's THAT kind of thing . . ."

The problem was, what kind of thing? Blumenthal wanted to be Secretary of Defense, reports one economic specialist. Then he thought, maybe it would be Commerce. But another person claims that no - he heard a rumor Blumenthal wanted State . . . Effects of Power

One time - this was when he was already in the Treasury - Blumenthal and an aide were disagreeing over something.

"You know," the new Secretary told him mildly, "you were not my first choice for this job."

He does have a way of telling you what's on his mind. Not even the President is immune from that.

When the Secretary saw how the energy package was coming along, he became so concerned over its ecomonic impact that he called Charles Schultze over to his office. Together they decided to place a call to Carter. Blumenthal told Carter that he and Schultze had concluded there were still a lot of unanswered questions about that energy program.

"I thought when you and Charlie are together, you knew everything," Carter told him drily.

And Blumenthal replied, "Well, we know what we don't know."

"If you're an imperious character," says one of his old friends from Bendix, 'in a hurry and running a big machine, you exude an aura that makes the best of your associates tend to bow to the wind. He's aware of that. He knows the effect power produces on people."

Yes, a man whose favorite reading includes biographies of Napoleon, Woodrow Wilson, FDR and John LeCarre novels just might know the effects of power.

And yet - he says this, and one senses it is true - he does no want the publicity that often attends power.Like many executives, he enjoys anonymity. Three months ago he walked into a New York store and tried unsuccessfully to make a purchase with a check.

Well, now all that's changed.

"I walk into a store, people recognize me right away. "Oh, how ARE you, Mr. Secretary . . .'" he mutters. "I hate to get into an elevator and have people talk to me. I cannot understand how people enjoy notoriety. Or fame. Or the Secret Service."

And so Michael Blumenthal is asked what would happen. What would happen if the fame, the title, the money - all of it - were stripped away from him, and he had to start over from nothing. Once again, He is asked, could he survive this time too?

"Well, I would certainly know what's important in order to survive. I would know the risks. And I have kept a sense of proportion in my attitude toward position and things. They don' mean that much.

He stops, Thinks, Reconsiders.

Finally, he says, "The reason I hesitate is because at age 51, one is a different person than at 20, you know. If, you take people in my situation, I'd come out average or above-average. But yeah, I think I could survive."