His blue pinstripe notwithstanding, there is no confusing Socialist Pierre Beregovoy with the men who preceded him as secretary general of the Elysee Palace since the Fifth Republic was founded in 1958.

Although a minority of those who have served as chief of staff for French presidents since Gen. Charles de Gaulle's tenure have risen from humble circumstances, Beregovoy alone started out as a manual laborer.

He is the only one not to have gone to one of the grandes ecoles, those highly selective schools whose graduates staff the top echelons of Frenmch government and business.

Beregovoy's predecessors range from Jacques Wahl, the son of an immigrant tailor, to Foreign Trade Minister Michel Jobert and such aristocrats as Etienne Burin des Rosiers and Geoffroy Chodron des Rosiers and Geoffroy Chodron de Courcel, both of whom came from the diplomatic service and went on to become ambassadors.

The real difference, however, is the warmth and informality of manner of this small, 55-year-old politician who thinks nothing of dropping the slightly common expletive quoi -- meaning roughly "right?" -- into his conversation for emphasis.

Asked if he thought his presence symbolized the Socialists' goal of democratizing French society, he said: "I hope so. I probably am closer to people, strike them as more authentic."

He did not complete the comparison, but left the definite impression that he was talking about the clever, highly educated technicians and advisers who are part of any modern society's governmental inner circle.

Son of a Ukrainian Jewish immigrant and a Norman woman, Beregovoy finished grade school and at 15 was oiling mill machinery before taking part in the liberation of France alongside American and Canadian infantrymen as a teen-age resistance fighter.

His only other formal education was a few months many years later at a special school for trade union officials at the Law School in Strasbourg.

During a recent interview, he suddenly started sketching the cogwheels he used to make as a teen-age metalworker, explaining that his love of mathematics made that kind of job easier in the days before such machinery was automated.

Could a person with so little formal education get as far as he had in today's France?

"Probably not," he replied. "Today you'd need at least a bachot," slang for baccalaureat, or the high school degree awarded after a tough nationwide examination that is the passport to higher education.

That set him off dreaming out loud about what the Socialists want to accomplish.

"If our professional training works, why not, why shouldn't someone like me make it? The big problem is awakening the mind. I know we are told it's the first three years that count, but we should be doing something to awaken those between 15 and 19."

With the backdrop of a Directoire desk stacked with files and a Gobelin tapestry on the wall, Beregovoy traced his career through a subsequent job with the railroads to Gaz de France, the nationalized utility where he rose from glorified salesman to head of the publications department.

There he learned how to turn complicated technical gobbledygook into understandable phrases.

President Francois Mitterrand, himself an author noted for his writing style, often tells Beregovoy: "Translate this supersubtle note into plain language." One of the jobs the new presidential secretary likes most is explaining policy decisions after the weekly Cabinet session.

As a trade union activist, Beregovoy was dealing with bosses by the time he was in his early twenties, and he also boned up before such encounters.

"Trade union work and politics obliged me to read and write a lot to keep abreast," he said, "and what forced me to learn to take notes and synthesize my ideas.

"I had to learn at 30 what the enarques [the nickname for graduates of the prestigious national public administration school] learned when they were studying to get into their grandes ecoles."

He climbed the rungs of the various small groups that survived the decline of the old Socialist Party during the ill-fated Fourth Republic.

Beregovoy shares with his boss a predilection for politics.

"I deal with enarques and I am struck that they want me to discuss politics," he said, "not technical matters, which are details they know better than I do in any case."

Even his adversaries credit Beregovoy with a tough negotiating style belying his salt-of-the-earth exterior.

The Communists discovered this when he was the Socialist negotiatior involved in updating the initial, common political platform the two parties signed in 1972.

Both parties wanted to call the shots. In retrospect it seems clear that the breakdown of those tough discussions in 1977 marked the first time the Socialists began outdistancing the Communists as the premier party of the French left and even of the French working class.

"He's no intellectual giant, but they've got no lack of super brains in the party," an old friend said, "and he' a good organizer and he's as anticommunist as they come."

His other long suits are loyalty and discipline. Furthermore, in the whole Mitterrand inner circle he is one of the rare aides who is what the French call du terroir, or smacking of the soil.

Hje regrets not knowing foreign languages, a failing he shares with Mitterrand.

"But in a way that's an advantage," he mused, "because it gives you time to think while the interpreter works."

His only major trip to the United States took place in 1977, when he spent a month visiting places like Sioux Falls, S.D. -- "I wanted to see how an American small city worked" -- and The Washington Post's daily editorial meeting -- "They were out after some senator who was flying his girlfriend around the country at government expense."

Beregovoy spoke of the fraternity of arms at the liberation of France so many summers ago, how both the Soviet Union and the United States were loved and honored here then.

"At the liberation we thought we were going to create a new society," he said. Obviously he feels that now the Socialists have the chance -- and obligation -- not to let that chance slip by again.

Carried away by his recollections, he had let the interview run on too long. He sheepishly excused himself and explained, "My next visitor is Bernard Tricot, one of my predecessors in this job." Today Tricot runs the archestablishment stock market watchdog commission.