A mentally retarded man whose identity has baffled police since he was found sitting on a curb in Glen Burnie, Md., last month may be a step closer to home.

The FBI has matched the fingerprints of the man, who told police his parents abandoned him, with those of a man who was fingerprinted in California three years ago.

Anne Arundel County police, who are leading the search for the man's home, said yesterday he apparently once was in custody of police in San Diego. But they refused to release further details until a court order is issued in California -- probably on Monday -- releasing sealed documents there.

The man is believed to be about 21 but has the mental development of a 5-year-old. He told police when he was found July 8 that his parents left him at a Glen Burnie Burger King after telling him he couldn't go home with them. He also says his name is Jimmy Conners, that he had only been told his surname in February and that his parents were named Bob and Jacqueline.

Deans said yesterday he expects to receive police documents, hospital records and court and guardian-hip papers from California that should give the man's history until 1978. He said the name listed on California records is not Jimmy Connors and that at least one document lists the man's parents as "unknown."

With the information expected from California, Deans said, he hopes to work forward to learn how the man came to be found, apparently abandoned, in Glen Burnie. "We have nothing to suggest," Deans said, "that Jimmy isn't telling the truth." He said someone has clearly looked after him in the three years since he was in California.

The man has been able to give investigators only vague clues to the location of his home, and although he recognized parts of Arlington when Anne Arundel Det. Gordon Deans and social workers drove him around the Washington area, he was unable to find his house.

The man is now staying at Crownsville Hospital Center, a state psychaitric hospital, until room can be found in a home for retarded persons. In an interview yesterday, he told a reporter he found it difficult to recognize his neighborhood in Arlington because "they all look the same". He said his father had not allowed him to go any further away from home by himself than a small nearby store. He didn't know the neighbors, he said, because his father told him never to speak to them.

He said he lives near a shopping center that has a pizza store, a "Ward's" store and a grocery store. He said he went swimming about two times a week at the Army-Navy Club, usually with a girl named Jenny, who was his babysitter. Jenny is Oriental, he said, and he believes she is a student at Georgetown University.

He also said his father had been teaching him karate in the basement of their home and that his collar bone and a leg were broken during the lessons, which he said began when the family was living in California.

He said he thought the reason he was abandoned was that he threw a 2-year-old child named Paul, apparently adopted by his parents, up in the air and dropped him. The child broke his leg in the fall, the man said. He showed no resentment towards the couple who he said abandoned him: several times during the interview he said he wanted to find his "daddy" and that he wanted to leave Crownsville and go home.