In what may be the Watergate scandal's last gasp, lawyers for former President Richard M. Nixon's estate yesterday demanded as much as $213 million for the government's seizure of his tapes and papers -- and were promptly accused of a crass effort to "cash in" on records reflecting "the worst abuses of power in governmental history."

Opening a trial that Nixon first sought 18 years ago, the Nixon attorneys compared the tapes, which led to his downfall, to the Gutenberg Bible and the Declaration of Independence and described them as the prize of a collection worth $35.5 million in 1974 dollars, the year Congress ordered confiscation. They also are seeking compound interest, which could increase the award sixfold.

The Justice Department fired back indignantly, charging that the Nixon camp was relying on "wildly inflated" appraisals riddled with "methodological flaws." Neil H. Koslowe, who argued the case for the government, said the estate should be paid nothing at all in light of Nixon's intent to keep the collection intact as "an integral historical archive for researchers."

The Nixon attorneys, Koslowe protested, "want the American taxpayers to pay for material and tapes that reflect the worst abuses of power in governmental history. It would not be fair, it would not be equitable, it would not be right to pay for material reflecting governmental crimes. It would be an outrage."

Nixon lawyer R. Stan Mortenson, by contrast, described the lawsuit as a case brought reluctantly, by a former president denied his dream of seeing his papers in a traditional presidential library at a site of his choosing but at least entitled to compensation under the provision of the Fifth Amendment covering takings of private property for public use.

"Mr. Nixon, and now his estate, seeks no windfall," Mortenson said in his opening statement in federal court here. "What he seeks, even after having departed the scene, is just compensation."

He said "close to $5 million" of the anticipated award would go to Nixon's daughters and heirs, Julie Nixon Eisenhower and Tricia Nixon Cox, for legal expenses Nixon incurred in past years to "vindicate his rights," while "an agreed upon" percentage would be paid to Mortenson and his law firm, Miller, Cassidy, Larroca & Lewin. The rest would go to the privately run Richard Nixon Birthplace and Library Foundation in Yorba Linda, Calif., where Nixon's pre- and post-presidential papers are housed.

Mortenson would not disclose the percentage to be paid in legal fees. "It's a contingency case," he told a reporter.

The trial, a battle of experts that is expected to last about two months, is taking place without a jury before U.S. District Judge John Garrett Penn, who once held that Nixon was custodian of his records as "a trustee for the American people" and not entitled to payment. An appellate court panel disagreed, holding that every president since George Washington had treated his presidential papers as private property and sending the case back to Penn "for a determination of compensation due."

Voicing confidence in the estate's experts, Mortenson said one key witness would put the "fair market value" of the tapes, which he described as a "rare cultural icon," at $12 million at the time of the taking.

He said other experts would value the 44 million pieces of paper in the Nixon collection at the National Archives complex in College Park at $10.9 million, the million feet of motion picture film at $8.5 million, while the sale of photographs and other fees, such as rights to publish the contents of the tapes, would bring the total to $35,558,000 in 1974 dollars.

Other witnesses, such as historian Stephen Ambrose, would talk about the value of files within the files, such as news summaries annotated in Nixon's handwriting and reflecting his "thoughts and emotions," Mortenson said. He said Ambrose would describe these materials as "the heart of what you're looking for as a historian."

Koslowe scoffed at the estate's piecemeal approach and said it was absurd to think that Nixon would have been able or willing to sell all his tapes in 1974 when they were "presumptively classified," often of poor quality and untranscribed, and locked up by the Secret Service. Koslowe reminded the court that Congress confiscated Nixon's records by law to prevent him from destroying the tapes, as an "infamous" agreement Nixon had signed with the General Services Administration would have allowed him to do.

"Who are they kidding?" Koslowe said of the Nixon camp. "Mr. Nixon is entitled to zero compensation." He said Nixon himself stated proudly at a 1973 news conference that "in all my years of public life, I have never profited . . . from public service" and yet now his estate was seeking to "cash in on documents created by public officials at public expense on public equipment."

If the court should still want to entertain the idea of "piecemeal" sales, Koslowe said government experts would testify they would bring, at most, $2.2 million, primarily "from the Watergate-related material and the tapes."

The first witness was Karl Weissenbach, acting director of the National Archives' Nixon project, who said the staff there has opened to the public only about 7 million of the 44 million pages of textual materials and 427 hours of the 3,700 hours of tapes, largely because of the delays caused by legal wrangling with the Nixon camp.