What was going on when I was born?

The International Harvester Company, continuing to pare down in its desperate bid for survival, said today that it had reached an agreement to sell its money-losing construction equipment business to Dresser Industries, a diversified supplier of industrial products and services. Dresser is now caught in the middle of a dispute between the French Government and the Reagan Administration over the sale of equipment for the construction of the controversial gas pipeline from Siberia to Western Europe. The companies did not disclose terms of the sale, but Wall Street analysts said that Dresser would pay about $150 million in cash for the Harvester division. Cash-starved Harvester said the unit had assets of about $580 million, meaning the company would take a big write-off.

The ramp of their low, gray landing craft tapped the quay in Beirut harbor just after dawn today, and United States marines, holding their automatic rifles out in front of them, stepped briskly onto Lebanese soil. For the second time in 24 years, the Marines had landed in Lebanon, this time as part of the multinational force to monitor the withdrawal from west Beirut of the Palestine Liberation Organization's guerrillas trapped there by the Israeli Army. In Full Combat Dress The first 210 debarking marines, of the 800 who will help control the withdrawal, were in full combat dress, their dark green mottled uniforms hung with field packs, spades and ammunition. The young men, looking straight ahead with their helmets low on their foreheads, strode quickly and silently to their positions around the waterfront, where another contingent of guerrillas was due to depart in a few hours.

A Federal judge has found a sheet-metal union local and a group of 121 companies in contempt of court for ''willful disobedience'' of an affirmative-action order to increase the number of nonwhite sheetmetal workers to 29 percent. The defendants were fined a total of $150,000. It was only the second such contempt ruling in eight Federal antidiscrimination cases involving construction unions in New York City in the last 10 years, according to James F. McNamara, the director of the city's Office of Construction Industry Relations. It marked the first time that fines were imposed by the court.

International Israel has begun to release ''sizable'' numbers of the 7,000 Palestinian and other detainees held in southern Lebanon since the Israeli invasion began June 6, according to officials in Jerusalem. The development was one of several that suggested that Israel was now reducing the scope of its operation in Lebanon. (Page A1, Column 1.) American Marines entered Lebanon for the second time in 24 years. The first group of a contingent of 800 marines joined French troops as part of the multinational force that is monitoring the withdrawal of Palestinian guerrillas from west Beirut. (A1:2-3.)

The Democratic candidates for lieutenant governor, County Executive Alfred B. DelBello of Westchester County and Carl McCall, disagreed yesterday on capital punishment, the Westway project, Mayor Koch and other issues. The range of views, offered in a debate at The New York Times, was unusual, since the two Democrats have have no clear-cut ideological conflict. The differences appeared early in the 90-minute meeting, when Mr. DelBello praised Mr. Koch's ''outstanding job as Mayor.'' Mr. McCall, although saying that he did not want to dwell on the Mayor's record, declared that ''much of what he takes credit for was done by the Legislature.'' Mr. McCall, a former State Senator and a member of the United States delegation to the United Nations in 1979-80, has not said whom he would prefer to see as the Democrats' gubernatorial candidate. Mr. Koch and Mr. DelBello have thus far campaigned as a ticket.

The Exxon Corporation, saying that it did not expect an upswing in the declining demand for gasoline, announced yesterday that it would close 850 service stations in the Northeast and Middle West and sharply reduce production capacity at its major New Jersey refinery. The announcement by the world's largest oil company marked the latest retrenchment in a year of sharp earnings declines, large reductions in capital spending and the elimination of exploration programs here and abroad. And while analysts said the action to reduce retail operations was only a small step in a sweeping, industrywide effort to cut costs, Exxon's move made it clear that even the oil industry leader expected severe, enduring difficulties. ''Over the long term, we see demand for petroleum products in this country leveling off and perhaps declining,'' said Les Rogers, a spokesman for Exxon U.S.A., the company's principal United States subsidiary.

The United States, even as it is becoming homogenized in some respects, is becoming more diverse in others, according to an emerging body of evidence. Data from the 1980 census, subsequent surveys of the population and studies conducted by organizations show that personal income and population distribution are tending to even out. But age distribution, poverty, housing, taxing capacity of states and numbers of foreign immigrants vary sharply from region to region. In some cases, diversity among the regions is greater than in the past. And the data show that the West has emerged with advantages over the other regions in level of education, in proportion of young people, in numbers of people with high incomes and in extent of wealth in the earth.

Mexico's financial crisis will force it to sharply increase oil production, a move that would put additional downward pressure on world oil prices and pose fresh threats to the cohesion of the Organization of Petroleum Exporting Countries, according to the views of several energy specialists. These analysts acknowledge strong political pressures within Mexico to husband what is widely regarded as its national treasure. But they say that the country's leaders may well decide to solve Mexico's foreign debt problems by raising exports by as much as 1.3 million barrels a day by 1985, to 3 million barrels. The country now exports about 1.7 million barrels a day out of a total estimated production of nearly 3 million barrels a day.

In 1961, the Glenn L. Martin Company, famous for its Martin Marauder B-26 bomber of World War II days, was moving rapidly into the developing missile industry when it merged with the American Marietta Company, a conglomerate with interests in cement and chemicals. Wall Street scoffed - missiles and cement? The Martin Marietta Corporation ignored the raised eyebrows and plunged ahead to develop a reputation for excellence in both the aerospace and cement businesses, according to analysts. That reputation, along with favorable earnings prospects, has Wall Street doubting that the Bendix Corporation will be sucessful in its attempt, announced yesterday, to acquire the company for $1.6 billion, or about $43 a share. ''It isn't exactly an exorbitant price,'' said Wolfgang H. Demisch, an analyst with Morgan Stanley & Company. ''We are looking at a company where the prospects for earnings are very good and the offer is $8 less than where the stock sold last year. It doesn't even offer investors who have been participating in the company for many years an offer where they can get even and get out.''

Israel has begun to release ''sizable'' numbers of the 7,000 Palestinian and other detainees held in southern Lebanon since its forces swept through the area to Beirut, officials here said today. Those being released, a military spokesman said, ''were generally passive members'' of the Palestine Liberation Organization who did not represent security risks. This development, which officials here said had no connection with the withdrawal of Palestinian guerrillas from west Beirut, appeared to be one of several actions indicating that Israel was reducing the scope of the operation in Lebanon that began with the invasion of June 6. Shifting of Forces Reported Reports circulated here that Israeli military strength around the Lebanese capital was being reduced. Those reports, which included accounts broadcast by the state radio, said that Israeli forces were moving south in large numbers and that convoys of tanks and armored personnel carriers were causing traffic jams on the road between Beirut and Sidon.

Representative Frederick W. Richmond pleaded guilty yesterday to tax evasion and two other Federal charges and agreed to resign immediately from the House of Representatives and not seek reelection in Brooklyn's 14th District. He said the actions to which he pleaded guilty had been ''irresponsible, unnecessary, foolish and wrong.'' In an unusual plea bargain that capped an eight-month Justice Department investigation, Mr. Richmond admitted having deliberately under-reported his 1980 Federal income tax by nearly $50,000, having possessed marijuana cigarettes obtained from his Congressional staff and having made an illegal $7,420 payment to a Navy employee who had been helpful in obtaining Government contracts for the former Brooklyn Navy Yard. Sentencing on Nov. 12 The felony tax charge and the two misdemeanor charges carry combined maximum penalties of up to seven years in prison and a $20,000 fine. Sentencing was set for Nov. 12.

The forced liquidation of Banco Ambrosiano, the biggest bank collapse in Italy since World War II, has embarrassed the Government and the central bank. But they have at least gained from it a useful weapon in continuing efforts to exercise tighter control over the Vatican's financial affairs, long a sore point. Since the failure of Ambrosiano earlier this month, following the default of its Luxembourg subsidiary on $400 million in loans, Italy has stepped up its negotiations with the Vatican. The aim is twofold, according to officials of the Treasury Ministry and Banca d'Italia: to urge the Vatican to improve surveillance of its broad financia*of the Vatican bank is Archbishop Paul C. Marcinkus of Cicero, Ill. He has taken the unusual step of denying any impropriety in the Vatican's relationship with Banco Ambrosiano. The highest-ranking lay official is Luigi Mennini, who is under investigation by the Italian authorities because of the bank's earlier dealings with Michele Sindona, the Italian financier now in jail in New York.