The North American Plating Co. opened for business in suburban Des Plaines on Jan. 30, 1979, with explicit instructions for its trimly dressed staff.

"Business attire has to be worn to, from and while outside the office," they were told. "Guns, handcuffs, bullet pouches, etc., are to be in a brief case or some suitable container . . . . Due to the volume of calls to be intercepted, . . . it will be necessary to bring in lunch and other necessities."

The "businessmen" were actually FBI agents embarking on grueling 12-hour shifts for what turned out to be the most extensive electronic surveillance operation ever conducted under federal law.

The results are expected to start unfolding in U.S. District Court this week with the trial of five men on charges of conspiring to bribe a United States senator, Howard W. Cannon (D-Nev.).

The most prominent defendant is Roy Lee Williams, 67, plain-spoken president of the International Brotherhood of Teamsters, the biggest, most powerful union in the country.

Assailed by a Senate subcommittee as a tool of organized crime, Williams is the third Teamsters president in the last 25 years to face felony charges in a federal courtroom. He was elected by acclamation at a Las Vegas convention in June of 1981 and awarded an annual salary of $225,000 less than two weeks after his indictment. He has denounced the charges against him as "a damn lie."

Scheduled to stand trial with him are:

* Allen M. Dorfman, 59, a millionaire insurance executive whom the FBI has described as "controlled" by Chicago's La Cosa Nostra.

* Reputed mobster Joseph (Joey the Clown) Lombardo, 53, a frequent visitor at Dorfman's insurance offices in the Teamsters' Central States Pension Fund building here and allegedly Dorfman's link to the crime syndicate.

* Andrew G. Massa, 65, a former trustee of the $3.5 billlion Central States Pension Fund and now labor relations director for both the pension fund and the Central States Health and Welfare Fund.

* Thomas G. O'Malley, 46, a trucking company executive and one of the four employer trustees of the pension fund.

Cannon, who is seeking his fifth term at age 70, has not been charged and he has denied any wrongdoing or impropriety. At one point during the inquiry, the FBI's Chicago office told Washington in a special hand-carried report that it believed it had "sufficient probable cause" to start tapping the senator's phones, but permission was never granted. Government prosecutors have said in formal pleadings that Cannon "may be shown by the evidence at trial to be" an unindicted co-conspirator, but he was not named as one. Defense lawyers are planning to call him as a witness.

The 11-count indictment accuses Williams and the four others of conspiring to bribe Cannon by promising him exclusive rights to buy a valuable piece of the Pension Fund's Las Vegas real estate at a below-market price.

In return, according to the government, Cannon was to help defeat legislation that sought to deregulate the trucking industry by steering the bill to the Senate Commerce Committee, of which he was chairman, and squelching it.

The Las Vegas real estate was sold to others, and Cannon later introduced and helped pass a trucking deregulation bill in 1980. The senator offered the bill just a few days before news leaked out that he was under FBI investigation.

All the defendants have pleaded not guilty. In a rare interview with the Chicago Sun-Times, Williams said recently that he was confident he would be exonerated. He has been indicted three times before in connection with Teamster activities. He was acquitted twice and the charges in the third case were dismissed.

As for alleged links to organized crime, the blunt Teamsters president told the Sun-Times that he doesn't know mobsters, but he can smell an FBI agent.

The new indictment, in any case, was an unexpected byproduct of the undercover operation that the FBI had plotted. It was called "Operation Pendorf" and its aim was to "penetrate" hidden interests that Dorfman had allegedly acquired and was trying to acquire in a number of Las Vegas gambling casinos.

A five-page FBI memo dated Jan. 23, 1979, seven days before the telephone surveillance of Dorfman's Amalgamated Insurance Agency was started, summed up the suspicions.

"Allen Dorfman has wielded power over the Teamsters Central States Pension Fund for many years, through the influence, originally of his father, 'Red' Dorfman a union organizer with allegedly close ties to Chicago mobsters and former Teamster boss James R. Hoffa," the memo said.

"Dorfman," the document continued, "is controlled now by the Chicago LCN La Cosa Nostra , specifically Joe Lombardo, and has continued to make huge sums of money available to organized crime throughout the country on a continuing basis. One method of obtaining this money is for Dorfman and others to buy casinos in Nevada using front men and then insert their own key personnel to effect a skim. This skim money is then transferred to organized crime figures. The primary objective of this wiretap coverage is to obtain evidence of this hidden ownership and skimming procedure."

Prosecutors from the Justice Department's Chicago Strike Force secured a court order approving the wiretap on 13 phone lines at Dorfman's insurance offices on Jan. 29, 1979. In a secret 70-page affidavit, FBI agent Peter J. Wacks told the court of a half dozen confidential informants and one named informant -- Jimmy Fratianno, the highest-ranking Mafia member ever to turn government witness -- who had asserted that Dorfman and his associates were involved in illegal activities.

One of them, "Confidential Informant No. 1," was described as "a prominent organized crime figure" who had assisted the FBI in 15 investigations in the past year and who "has never been found to be inaccurate." He reportedly asserted that Dorfman "represents the Chicago and Kansas City organized crime groups dealing" with the Central States Pension Fund and for a number of years had a hidden interest in the Slots-A-Fun and Bingo Palace casinos in Las Vegas.

Another man, "Confidential Informant No. 3," who was said to have been a business and social associate of Dorfman for at least 10 years, said that Dorfman had close ties with Kansas City crime boss Nicholas Civella. This informant also said Dorfman had a hidden interest in the Slots-A-Fun casino.

Fratianno, a one-time crime family boss, described Dorfman as "the property of the Chicago family" and asserted that Dorfman paid kickbacks to Lombardo out of the exorbitant fees that Dorfman got for insurance contracts on various Las Vegas casinos.

FBI agents began monitoring Amalgamated's phones, the day after the court order was signed, from "North American Plating," at 1400 E. Touhy Ave. in Des Plaines, about two miles from the Teamsters' Pension Fund building. The volume was heavy. They intercepted some 830 calls that first day, 36 of which were marked with red asterisks on FBI logs as potentially "pertinent."

Nothing came in about the Bingo Palace or Slots-A-Fun, but according to pretrial records and transcripts, there was one call that government prosecutors regard as especially significant. It was a conversation that at various points involved Dorfman, Lombardo, Massa and William Webbe, an Amalgamated Insurance official who has been named an unindicted co-conspirator. The discussion dealt in veiled terms with getting Roy Williams' approval of a plan to have Massa and O'Malley speak to someone about a "bid" that needed to be "handled."

(Williams at the time was a Kansas City-based international vice president of the Teamsters and had been a Central States Pension Fund trustee for 22 years until 1977 when he resigned under government pressure. As long ago as 1971, a special Labor Department report asserted that he was under Civella's control.)

At first, because of another call that was intercepted that day, the FBI thought that Dorfman and his associates were talking about the Aladdin Hotel and Casino in Las Vegas which was then up for sale.

The next day, Jan. 3l, the FBI picked up another call, between Webbe and Robert Bjornsen. He turned out to be Cannon's son-in-law, but FBI monitoring agents were to misspell his name for weeks as "Ornsen" and "Ewing" and even "Euing." The discussion implied that Dorfman had worked hard to get someone competing against Bjornsen to back out of the bidding. There was a mention of telling "the senator" about the situation. Again, FBI agents testified earlier this year at marathon suppression hearings, they thought the conversation concerned the Aladdin.

Finally, according to court records, the Operation Pendorf investigators realized that "the senator" was Cannon, that Bjornsen was his son-in-law and lastly, that the property in question had nothing to do with the Aladdin, where the asking price was some $90 million. Instead, the government says, the conversations concerned a vacant 5.8-acre tract near Cannon's home, a piece of Pension Fund real estate that the senator and his neighbors wanted to buy to fend off the threat of high-rise development.

According to his grand jury testimony in 1980, Cannon said he did speak with Dorfman about the matter at a meeting in the senator's Las Vegas office on Jan. 10, 1979. The Teamsters' Roy Williams and Ed Wheeler, a Teamsters lawyer from Washington, were also present.

"I told Mr. Dorfman -- I think it was on the way in, when I introduced him to my son-in-law -- that we were putting in a bid on that, or had put in a bid, one or the other, on that Pension Fund property," Cannon testified.

The senator said it was only the second time in his life that he had met Dorfman. He said the first occasion was in 1971 at a Nevada hotel where the operator introduced him to Frank Fitzsimmons, "who had apparently just been elected" Teamsters president, and to Dorfman.

The senator said he knew Dorfman by reputation. After all, Cannon observed, "the Teamsters have somewhere between $150 million and $200 million of loans in Nevada. And it was well known that he was associated with the Teamsters, and handled, I suppose, a good number of those loans."

(When news of the investigation first leaked out, in February, 1980, a spokesman for Cannon said the senator had sought out Dorfman to find out whom to approach about buying the so-called Wonderworld property. The spokesman said Dorfman directed Cannon to a Victor Palmieri & Co., a new firm in charge of investing Teamster pension money, but the $1.4 million offer was turned down.)

According to Cannon's grand jury testimony, the main topic of the meeting was the Teamsters' opposition to deregulation of the trucking industry and to steps being taken in that direction by the Interstate Commerce Commission. Wheeler, Cannon said, did the talking while Williams and Dorfman listened. The senator's son-in-law, who represented Cannon and other homeowners in the real estate negotiations, waited in an outer office with William Webbe, the grand jurors were told.

Government prosecutors were openly skeptical of Cannon's testimony. At one point, the senator denied making any commitment to Dorfman or Roy Williams about his position in Congress on any matter and denied that Dorfman or Williams had made any commitment to him about the Wonderworld property. On hearing that, the prosecutors played back part of a conversation between Roy Williams and William Webbe:

Webbe: "And he did."

Williams: "Yeah, and he got the bill out of Kennedy's hands."

Webbe: "That's right, he did everything he said."

The senator remained steadfast in his denials, declaring that "if you trace the legislation, you'll see that there couldn't have been any commitment made."

Plans for the original deregulation bill, backed by President Carter and sponsored by Sen. Edward M. Kennedy (D-Mass.), to end government-sanctioned price fixing in the trucking industry were announced with fanfare in January, 1979. On Feb. 7, with the bill still to be introduced, Cannon took to the Senate floor to denounce Kennedy's Judiciary Committee for trying to grab the legislation. It was finally introduced March 21, 1979, after a compromise whereby Cannon's Commerce Committee got primary jurisidiction while Kennedy's committee waited in the wings for a 30-day review of the antitrust provisions, without right of amendment.

Cannon held hearings for the rest of the year. He introduced his own deregulation measure, a less sweeping proposal but one that he said was still "strongly opposed by the Teamsters," on Feb. 1, 1980. It was, coincidentally, the same day that the surveillance in Operation Pendorf ended.

Government prosecutors in Chicago reportedly recommended that Cannon be indicted but Carter administration officials concluded that the evidence was insufficient and Reagan administration officials saw no basis for overturning that decision. The indictment against Williams and the four others was lodged on May 22, 1981.

According to the indictment, part of the alleged conspiracy involved efforts to get other bidders on the Wonderworld property to withdraw. The prosecution team, headed by Chicago Strike Force Attorney-in-Charge Douglas P. Roller, has charged in court filings that this is what the Jan. 30 phone call involving Dorfman, Lombardo, Massa and Webbe was all about.

The conversation also contains a specific reference to "Roy" as the individual who "ok'd it," and prosecutors say they will argue that this meant that Williams had approved the sale to Cannon. As a result, the government contends, Lombardo and Dorfman sent Massa and O'Malley "to see Allen Glick to convince him to withdraw his bid on the Wonderworld property."

A governmment informant, according to pretrial records, told the FBI a few days later about a meeting between O'Malley, Massa and Glick at the La Costa Hotel and Country Club north of San Diego later on Jan. 30, 1979. According to one account, Dorfman was also hovering about.

Glick, a San Diego lawyer and real estate salesman, became prominent in the early 1970s when he became the biggest stockholder in several Las Vegas casinos with millions of dollars in loans from the Central States Pension Fund, reportedly as a front man for organized crime. Acccording to government records, Glick made a $1.6 million bid for the Wonderworld property on Jan. 17, 1979 and withdrew it through an intermediary on Jan. 31.

Defense lawyers over the past year have lodged stiff protests against the forthcoming trial, most notably during four weeks of suppression hearings last spring when they contended that the government had lied in getting extensions of the court-ordered surveillance. U.S. District Court Judge Prentice H. Marshall said it was "a very close question" in some respects, but ruled that investigators had not deliberately misled the judge who issued the orders.

Jury selection was scheduled to start last week, but Dorfman was hospitalized with chest pains at the last moment, forcing a postponement until today.

Once it gets going, the trial, with Marshall presiding, is expected to take eight weeks or longer. The government has said it intends to introduce 54 taped conversations, most picked up by telephone taps, some from bugs planted in Dorfman and Webbe's offices after the operation began.

The prosecutors have also served notice that they may seek to introduce recorded evidence of five other conspiracies, including one involving a hidden and illegal interest in the Aladdin, later in the trial. One May 1, 1979, conversation reportedly has Dorfman, Lombardo and Anthony Spilotro, reputedly the Chicago syndicate's overseer in Las Vegas, talking about the availability of the Aladdin casino because of the conviction of Detroit gangsters who had been tied to it.

Defense lawyers have assailed the rebuttal strategy and indicated they will fight it at every turn. As O'Malley's attorney, William G. Hundley, protested at a recent hearing, "it puts a bit of a cloud over defense counsels' case" if they have to worry about such tape-recorded retaliation for putting their clients on the witness stand.

The judge was noncommittal although he allowed that "it does add a degree of uncertainty to the case."