Harold M. Foster, a lawyer and cousin of Ms. Hall, said that after Mr. Altman's death on Aug. 15, 1985, he helped trace the underwriters who had paid Mr. Huberman. ''They, of course, are the owners of the violin,'' he said, referring to Lloyd's.M Ms. Hall, 69, said she met Mr. Altman in Washington in 1968 while awaiting a divorce from her first husband. They met at a restaurant where Mr. Altman was entertaining, she said, and he played ''Lara's Theme'' for her.

''He played it like a dream,'' she said. ''I became smitten. It turned out to be a long love affair. I call it now an obsession I had.''

She said Mr. Altman had been a first violinist with the National Symphony Orchestera in Washington and had played the violin at many social gatherings. She showed copies of autographed pictures to Mr. Altman from President Richard M. Nixon and Vice President Hubert H. Humphrey. A Guilty Plea

Ms. Hall said she married Mr. Altman in Las Vegas in March 1985, two days before he was to be sentenced in State Superior Court in Danbury, Conn., for sexually molesting one of her granddaughters. She said she married him, in part, because she wanted to regain ownership of her house, which was in Mr. Altman's name. ''I had nothing,'' she said.

He was sentenced to a year in jail on a charge of risk of injury to a minor. His attorney, Ralph Friedland, said Mr. Altman accepted the sentence to avoid putting the granddaughter through the trauma of testifying at a trial.

Four months later, Ms. Hall said, her husband was diagnosed as having stomach cancer and was moved from the Litchfield County jail to a hospital in Torrington, where he died.

At his direction, she said, she looked under the canvas cover of his violin case and found the news clippings about the theft of the Stradivarius in 1936. ''My God, what have I got here?,'' she recalled saying.