The three old pals gossiping over tea were talking about the mystery woman. She is forever tantalizing -- "a figure like a ballet dancer." In her 50s, she also is a generation younger than the widows they are used to seeing over meals.

"And she has a beautiful getup all the time," Leo Jacobs recalled.

The problem used to be that she would always come into the cafeteria with her escort, a silver-haired gallant in his 80s, and would talk to no one but him, until one day he died. Now she comes in alone, but still remains aloof, and none of the three has dared walk up and introduce himself.

"We're all wondering about her," Leo said, nodding his gray head toward his brother Henry and their friend, Myer Sirotto, 75.

This is the way conversation goes in the Concord Cafeteria, a cherished watering hole for the legion of retired elderly who live in Miami Beach.

Other restaurants attract retirees, too, but none with the regularity of the Concord.

Except for a few Latin American tourists, looking out of place in their shorts and smooth skins, the clients are old, stooped and wrinked.

Their thrice-daily gatherings at the Concord dramatize the extent to which Miami Beach is a haven for elderly Americans. Thousands are Eastern European Jews who first fled Czarist pogroms to New York years ago and then more recently sought refuge here from harsh winters and middle-class neighborhoods gone to seed.

As part of an extensive investigation, The Miami Herald recently estimated that the southern end of Miami Beach -- 232 blocks from 21st Street to the southern tip of the island--is home to the nation's oldest population.

The 1.74-square-mile area contains 50,000 inhabitants, including 15,000 elderly Jews.

They can be seen any early evening strolling painstakingly down the sidewalks or sitting on the terraces of hotels that line Collins Avenue with advertisements for monthly rates and "pullmanette" rooms including a corner to cook in. Or they can be seen sitting around the Concord, stretching breakfast into the morning, $3.26 lunch into the afternoon and $4.01 dinner into the night.

"It's like a social here," Myer told a visitor. "Everybody knows everybody. And you can hang around here. In other restaurants, you have to eat, pay and get out."

Leo joined in: "Some people stay here all day. The nucleus, they stay here all day." Sam, whom Leo described as "a worldly man," is part of the nucleus. He shows up at opening time, 6:30 a.m., and passes many an evening seated at a Concord table with a cup in his hand.

Sydney Schwartz, who manages the Concord for its elderly owner, complained that this attitude is the reason the Concord is the only establishment of its kind left in Miami Beach, where he said nine used to flourish.

"People come in here and buy a meal and sit for hours," he said. "If you try to talk to them about it, they say they spent $1.75 and they want to digest their food."

Sydney's complaints have a sweet edge to them, however. When he helps a turbaned, heavily made-up woman find her tray, he smiles and addresses her as "darling."

"You see those two?" he gestures toward a pair of stooped women walking toward a table and shouts greetings to them in an Eastern European language.

"They're Hungarians. I just introduced them half an hour ago and now they're already talking together."

Back at Leo's table, the conversation is still going. Leo, a former securities salesman for a New York firm, and Henry, a trucking dispatcher in his Bronx days, have no plans to go to the dance starting soon down the street. But Myer, who owned a drugstore in Philadelphia until he retired 25 years ago, cuts a mean figure on the floor despite his years.

Leo has another idea for the evening.

He will visit his 92-year-old friend at a high-rise a few blocks north. "There are 1,100 apartments in there," Myer declared, leaning forward, "and 700 single women."