A 27-year-old Pennsylvania man sought in connection with the Jan. 5 armed robbery in which a solid gold statue valued at $47,500 and assorted pieces of jewelry were taken from an artist's shop in Montgomery County has surrendered to authorities in San Diego, Calif., law enforcement officials reported yesterday.

Kenneth Montgomery, described by authorities as an unemployed drifter, turned himself in Monday night at an FBI field office in San Diego after a month-long manhunt in the greater Los Angeles area, FBI officials said.

The surrender was the latest development in a strange caper that began in December with a Rockville artist's chance encounter with a well-dressed stranger on an Amtrak train. The encounter took a sinister twist in January when the stranger showed up at the artist's shop, pulled out a gun and robbed the premises.

Montgomery, a native of New Castle, Pa., is being held on a federal fugitive warrant in lieu of $100,000 bail, and has been charged with unlawful interstate flight to avoid prosecution. Federal and state authorities said they intend to extradite Montgomery to Maryland, where he will face armed robbery charges in Rockville.

If convicted, Montgomery could face up to 20 years in prison, police said. The jewelry and solid gold statue, meanwhile, have not been recovered.

The incident, as described by the victim, Robert N. Williams, combined all the best and shadiest aspects of a Dashiell Hammett mystery. Williams said he first met the stranger, who identified himself only as "T.J.," on a Washington-bound Amtrak train from New York.

Williams, owner of a jewelry design shop, said that when he mentioned he was a jeweler by trade, the man asked if he could visit Williams in Rockville to have a necklace designed.

Williams said he gave "T.J." his business card, and a month later, the man appeared at Williams' shop, Advanced Design Concepts, on Nebel Street. Apologizing for what he was about to do, the man drew a small-caliber handgun, tied up Williams and an assistant, and proceeded to loot the shop of jewelry and other valuables, Williams said. He added that the man also took a 568-gram, 18-carat gold statue of a nude woman with a market value of $47,500. At the time Williams was preparing to enter the fully insured statue, entitled the "Sunbather," in a New York City art contest.

At first Montgomery County police considered the crime so implausible they asked Williams to take a lie-detector test. Williams did so and passed. At that point the FBI was called into the investigation because of the possibility that the statue had been transported across state lines.

Last month Williams identifed the stranger from a photograph furnished by the FBI. Upon learning yesterday of Montgomery's arrest, Williams said, "I feel so good I'm going over to buy a bottle and get drunk . . . I'm just really relieved that a lot of the blame has been taken off me."

Despite an insurance company's offer of a reward of 10 percent of the recovery value of the "Sunbather," no one has come forward with the statue, FBI officials said yesterday.