Born Sherman Suchow and brought up in Brooklyn, he transformed himself into the cane-carrying, British-accented Charles Merrill Mount and entered the international art world as a promising author and portraitist. But the metamorphosis was flawed.

Today, the art historian, who has left behind a trail littered with lawsuits, debts and estranged relationships, is in the 174-year-old jail at Salem, Mass., after his arrest last week in connection with a still-unfolding case involving rare historic documents apparently taken from national collections in Washington.

Somewhere between Brooklyn and the Salem jail, the 59-year-old Mount created an image for himself that seemed a caricature of elegance.

Mount advertised himself in Connoisseur magazine 11 years ago as "the last of the international portrait painters" and as a "rare phenomenon in the art world today."

More recently, he became a familiar figure in Washington's hushed reading rooms, the impeccably dressed scholar working on his latest book. Even in the slightly shabby, inexpensive Capitol Hill rooming house where he lived most recently, neighbors recall his love of dapper clothes and scholarly books and his British accent.

"An accent like that doesn't come naturally to somebody born in Brooklyn," said an art dealer who tried but failed to sell Mount's paintings. " . . . It takes a bit of thought to understand a man like that. It's hard to understand what is an act and what isn't. Maybe he lives in a world all his own."

Last week, Mount was arrested by FBI agents at a Boston bookstore in connection with the attempted sale of rare letters written by Abraham Lincoln, Winston Churchill and others, which were apparently stolen from manuscript collections at the Library of Congress and the National Archives.

Agents seized 100 documents from Mount in Boston, and, according to court records, they discovered a new cache of 162 historical documents Friday in a Washington bank safe deposit box maintained for Mount. The value of the documents is estimated at more than $150,000.

Charles McGinty, a court-appointed attorney for Mount in Boston, said federal authorities have no proof that the documents found in Mount's possession or in a safe deposit box were from national collections.

Mount declined through McGinty to be interviewed, but a portrait of his life emerges from interviews with those who know him and from legal records and prefaces to his art biographies.

"In the late '60s, his wife left him and things started going wrong about his career," said John Manship, a Gloucester, Mass., artist and friend for 30 years, who has agreed to post a $1,500 bond for Mount. "He has a kind of acerbic personality and makes enemies. It is all unfortunate."

Manship said he met Mount in his book-writing days in Europe during the 1950s. After studying history at Columbia University and the University of California at Los Angeles, Mount won a 1956 Guggenheim fellowship. In addition to painting landscapes and portraits -- most notably that of former Mississippi senator James O. Eastland in 1978 -- Mount wrote three biographies of artists, publishing one on painter John Singer Sargent in 1955, a second on Gilbert Stuart in 1964 and a third on Claude Monet in 1967.

His Monet biography was overshadowed a month after its publication by a raging dispute in the art world that was played out in headlines in London and New York City. The dispute follows Mount even to this day.

In September 1967, the Sunday Times of London printed an article that called into question Mount's authentication and sale of 14 works to a prominent London gallery, according to an account in The New York Times. The works -- authenticated by Mount as genuine Sargents -- were termed fakes by a panel of art experts, according to the account.

Mount called the charges "scandalous and scurrilous," and later filed a libel suit against the London newspaper, according to The New York Times. It is unclear how that lawsuit, filed in Dublin where Mount was then living, was resolved.

Manship recalled last week that the dispute left an indelible mark on Mount's life.

Manship said Mount also filed a lawsuit against some of the participants in New York. "Mount attacked back and went to court," Manship said. "I urged him not to pursue it. He made mortal enemies in the art world and the scholarly world."

With the collapse of his marriage to Sarah Long of Dublin, and his standing in the art world apparently damaged, Mount returned to the United States.

In the 1975 Contemporary Authors, Mount was identified as a consultant to the FBI on art forgeries and his "work in progress" was listed as "an exposition of fraudulent importation and sale of paintings attributed to John Singer Sargent." The book was never published.

Kenneth W. Rendell, a historic-documents dealer who identified some of the documents sold to the Boston bookstore as belonging to the Library of Congress, said he first encountered Mount in the 1960s. Mount, who was living in Dublin, contacted Rendell and arranged to buy some Sargent letters.

"The reason I remember him is he didn't pay his bill" of about $900, Rendell said last week. "Then he called me again in the mid-'70s. It was like he had forgotten his bill completely. He tried to sell the Sargent letters back to me."

Rendell said he never pursued Mount for payment of the debt, but other creditors were not so kind, according to court records in Maryland and Virginia, where Mount was a defendant in at least 10 civil suits for alleged failure to pay rent or long-term hotel bills.

In Montgomery County, he was arrested and criminally charged for failure to pay a $2,982 hotel and telephone bill at the Holiday Inn in Bethesda, where he lived for about two months in 1983.

The same year, he was found guilty of filing false statements in an application for a passport. He was placed on probation.

Mount's court battles suggest a portrait of a volatile, proud man who clung to his elegant self-image even as he descended into poverty. Fighting back, Mount filed countersuits against his creditors and even a suit against a State Department official, whom he accused of wrongfully taking Mount's possessions.

In that case, Mount presented himself as a prince in the art world and a pauper in life. His "name, published works, views and opinions, are found reprinted in the catalogues of the world's major museums," Mount wrote in the court documents.

A few pages later, he described being "left to wander the streets of Washington without clothing . . . without shelter and forced to eat by picking rotted apples and mouldy pies from a garbage bin behind a Giant market." Staff writers Laura Bischoff, Kristin Eddy, Marc Lacey and Dana Priest contributed to this report.