Special thanks to Dy Sheafor for contributing this article.
IT felt like a scene in an Edith Wharton movie or maybe even a Louis Auchincloss novel -- though the grand society author didn't seem to be taking notes on Wednesday amid the latest generation of old money in its 20's and 30's.
In a mahogany-paneled room at a private club on 43d Street, surrounded by books from the 1800's, Mr. Auchincloss was the host of a party filled with a high percentage of men with roman numerals after their names. There were women in black headbands and men in equestrian-print Hermes ties. There were Rockefellers, du Ponts, Fairchilds, a Roosevelt and a Vanderbilt.
But the guest of honor did not have an illustrious surname. He was Mark Gilbertson, a boyish, impeccabbly dressed figure, who has been like a well-connected, more worldly brother to most of the guests -- inviting them to parties, introducing them to future spouses, steering them through Fifth Avenue co-op boards.
''Mark didn't like the guy I was dating,'' said Andrea Lans, a party planner in her 20's, who attended the cocktail reception. ''I guess he didn't think he was right for me. He kept telling me, when I'm ready, he will introduce me to someone from a nice background with the same values. Last December, I was ready, and he introduced me to the best guy. I would trust Mark with my life. Really, I would.''
Meet Mark Forrest Gilbertson, known to friends and social chroniclers as the gatekeeper or Pied Piper of the offspring of New York's blueblood families and many of their not-so-blueblood friends. Anyone between 20 and 45 with an active social life in the Anglo-Saxon bastion of the Upper East Side has probably been introduced to Mr. Gilbertson or members of his Director's Council of the Museum of the City of New York -- whether through boarding schools, summers in Southhampton or the post-debutante party circuit.
Beyond that circle, Mr. Gilbertson and his 190 closest friends on the council are not really famous (except on the party pages of society magazines like Town & Country).
David Patrick Columbia, the editor in chief of Avenue, another magazine where their pictures appear, called Mr. Gilbertson a ''social impresario,'' comparing him with Earl Blackwell, the promoter of celebrities and founder of the Celebrity Service, and Ward McAllister, who compiled Mrs. Astor's list of the 400 in the 1890's.
Mr. Gilbertson, a product of the Lawrenceville School, Rollins College and vacations in Palm Beach, Fla., dislikes both comparisons. ''You are talking about a publicist and a secretary,'' he said. ''I'm part of the group. I just like hanging with my friends.''
By whatever name, Mr. Gilbertson, who is vague about his age but allows that he is ''40-ish,'' has played his role through the Director's Council, the museum's junior committee. Like the many other junior committees of museums and charitable groups, the Director's Council is in one way straightforward: it is a fund-raising arm of the museum for young donors, theoretically with less disposable income than their elders but with plenty of energy and a philanthropic urge.
But like all junior committees, the council is so much more: a floating cocktail party, a mixer for young singles from the right schools or families, an access point to society.
''When people join a committee they can have several agendas,'' said Kristina Stewart, the editor in chief of Quest, another Upper East Side magazine, which is filled with party pictures and listings for $5 million apartments. ''Some are using it as a social launch pad. Others use it to find boyfriends or girlfriends, and others are there because of their pure love of party dresses.''
Mr. Gilbertson's Director's Council, which he has run for 13 years, is not the flashiest junior committee. It does not give the most elaborate parties with the most glamorously dressed young women. But to many, it is the most socially coveted. An investment banker of 31, who is on three other junior groups but is desperate to be on Mr. Gilbertson's, cannot understand why he has not been asked. ''If I send $5,000 to the museum, do you think Mark will put me on?'' he asked. He did not want to be named for fear of seeming too pushy and spoiling his chances.
He was right to be concerned. Mr. Gilbertson insists that people cannot buy their way into his inner circle. ''Aggressive doesn't work,'' he said.
Robert McDonald, the museum's director, sounded bemused by it all. ''I'm amazed at the angst people have about trying to be part of it,'' he said. ''People are faxing their social curriculum vitae to the museum from around the country.''
The Director's Council, under Mr. Gilbertson, has helped raise $1 million over the years. Like the museum, the council evokes an older, staider New York. Its membership is a bulwark of traditionalism, embodied by restrained taste and preppie looks. The men hold jobs on Wall Street. The women often work as decorators (and nowadays, sometimes, lawyers).
''It's very about where you went to school, and did you summer in Southhampton?'' said Allyson Mitchell, 29, a nonmember who grew up on the Upper East Side and now lives in the East Village. ''It's not about being the hip crowd. They have dinner parties, then they go to bed.''
As adept as Mr. Gilbertson is at making introductions among his chosen few, he can be ruthless at excluding those who affront his standards. During a birthday party for him in January 1997 at Mortimer's, the clubby Upper East Side restaurant, he was hanging up his navy blue cashmere coat when four women with hair a shade too blond said hello. Mr. Gilbertson mumbled a reply, remarked quietly to a friend about ''cheapness'' and moved away.
''He never talks to me,'' one of the snubbed woman said later.
There are no fashion models, Hollywood stars or dress designers on the committee list for the museum's winter ball, which will take place on Thursday, the height of its annual social calendar.
As always, the black-tie ball, which this year celebrates the museum's 75th anniversary, is open to anyone with $120 for a ticket. Since attendance -- which includes drinks, dessert and dancing to the Alex Donner orchestra -- is the first step to winning entree to the Director's Council, the demand for the 1,000 tickets was strong, and they are sold out.
Then again, buying a ticket doesn't mean you'll feel welcome. It's an insular group, and the real action is not at the 9 P.M. ball but at 16 earlier private dinner parties given by council members, including one at an apartment in the Ritz Tower and others in the Park Avenue apartments of parents of the members.
''You see everyone you've ever known,'' said Andrew Roosevelt, 35, who has been attending the ball and its pre-parties since 1986.
Although it is a comfortable social cocoon for its members, the council is not closed to newcomers. It is possible to enter Mr. Gilbertson's world, provided that you are willing to assimilate, which means swearing off public displays of affection (and public displays of wealth), and embracing the Fair Isle sweater and the rep tie as the height of fashion.
Once one is inside the cocoon, the benefits can be formidable. When Andreas Vietor moved to New York a few years ago, Martha Vietor Glass, his aunt, handed Mr. Gilbertson her nephew's name and address. ''Mark put him on the list,'' said Ms. Glass, a descendant of an old New York family. ''I knew his social life would be taken care of.''
Bowen Farrell, a California native, moved to New York after receiving an M.B.A. degree from Harvard and met Mr. Gilbertson at the museum's winter ball. Two years later, he was on the committee. ''Mark makes New York feel like it's your own personal country club,'' said Mr. Farrell, who owns a leveraged-buyout company. ''You may know some people, but Mark knows everyone, and he brings them all together.'' He called Mr. Gilbertson ''the social conductor of the East Side.''
Others, however, snicker at the notion. Even in the Manhattan jungle in which Mr. Gilbertson is a social lion, there are plenty of other circles, and in many he is not a player at all. ''Why pay $75 or whatever to sit with a bunch of wannabes or the B-group people,'' said Jeff Klein, a friend and business partner of Adam Cahan, who is married to Samantha Kluge Cahan, the daughter of a communications billionaire. The East Side junior committee circuit is ''a social-climbing thing,'' he continued, adding, ''It's a lot of people whose parents want them to hang out with the right people, but the real social people in this city aren't that involved.''
By ''the real social people,'' he meant the young fashion-oriented nightclub set centered on Ms. Cahan and the well-married Miller sisters, (Pia Miller Getty, Alexandra Von Furstenberg and Marie-Chantal of Greece) who have been stars of the nightlife pages of WWD and women's magazines for more than a year.
Last July, W magazine dubbed Mr. Gilbertson's friends a ''lost generation'' of old-money heirs, who are no-shows at the city's A-list parties attended by power brokers from the news and entertainment media, fashion and business.
The article, which wounded some Director's Council members, was correct in one sense: the socializing of Mr. Gilbertson and his friends is usually private, conducted behind doors closed to most of the press. Typical among these events are cocktail parties that Mr. Gilbertson gives every other month for 80 guests in his town house apartment in the East 80's.
The routine is always the same: at 7 P.M., women in Chanel suits or black dresses and pearls and men wearing khakis and navy blazers ring the bell. A butler hired for the occasion stands at the door of the third-floor apartment to buzz people in and to make sure they sign the leather-backed guest book from Smythson of Bond Street.
Mr. Gilbertson, whose father is a surgeon and whose mother is a decorator descended from a family that owned choice New Jersey real estate, lives on a family allowance, he said, plus consulting fees for clients like the English specialty store Asprey and the design house Lilly Pulitzer, whom he advises about parties and charitable causes to sponsor. (''This is the group we're trying to target,'' explained John Asprey, the company's chairman. ''They get married. They have babies. They buy expensive gifts.'')
To ready his studio apartment, where he lives alone, for parties, Mr. Gilbertson has a bartender carry a plaid wing chair that normally occupies a corner to the nearby Frank E. Campbell funeral home. After the party, the bartender carries it back.
Despite the apartment's coziness, its high ceilings, mahogany-manteled fireplace and equestrian art give it the feel of a much grander space. When a guest arrives, bearing the traditional host's gift, Mr. Gilbertson sweeps over to say hello. He ushers the latest arrival into the room, interupts a group and makes an introduction.
''Do you know Marty Hale?'' he said to a group of four not long ago, presenting a newcomer. ''He's the chairman for the Young Friends of the Philharmonic. His party is next month. He's a good friend of mine and Allison's.'' (That's Allison Rockefeller, a chairwoman of the Director's Council.)
Mr. Hale, an investment banker, smiled shyly and joined the crowd.
It brought to mind something Edith Wharton wrote in ''The Age of Innocence'': ''If we don't all stand together, there'll be no such thing as Society left.''