Message to Chelsea Clinton: Come get your magnum of 1971 Cristal. It’s in the wine cellar at the “21” Club, and has been since your parents bought it in the late ’90s for use on your 21st birthday – a landmark that passed more than five years ago.

Ms. Clinton’s champagne is just one of 2,000 bottles that make up the famous “private stock” of the 77-year-old restaurant – bottles that were bought by the watering hole’s well-heeled regulars and stored away for future swilling. It sits near reds, whites, and bubblies earmarked for the likes of Elizabeth Taylor, Jackie Kennedy, Ivan Boesky, Jocelyn Wildenstein, and Governor Carey. Together they kill months, years, even decades until that day when their owners come and claim them.

“I’ve got bottles down here for people who had their 21st birthday 15 years ago,” the wine director and sommelier at “21,” Phil Pratt, said. So, I guess Ms. Clinton shouldn’t feel so bad for letting five years pass, then. But what about the 39 years a bottle of 1964 Chateau Lafitte-Rothschild has been waiting to bathe Liz Taylor’s lips in red? Or the vintages designated for President Nixon and Sammy Davis Jr., which will see their masters nevermore.

“That’s one of the biggest problems we have with this,” Mr. Pratt, who has pulled bottles at “21” for nearly 10 years, said. “Everything was initially done with Jack and Charlie” – meaning Jack Kriendler and Charlie Berns, the founders of the one-time speakeasy. “They did everything with friends. Everyone who came here they basically knew.” Fast forward a few generations, and tracking the far-flung and forgetful clientele of the private stock became trickier. “Say you and I were having dinner one night,” Mr. Pratt said, “and you had just had a baby and we’re getting trashed and I say, ‘I’m going to buy a bottle of Cognac and put it away for your kid’s 21st birthday.’ Letters are sent out as proof of the purchase. Father has the letter, but the kid doesn’t. He’s only six weeks old. As you grow up, if you don’t know the bottle is still here, it’s still here.”

A lack of negotiable cellar space led to the tradition’s discontinuation nine years ago. Still, attrition proceeds at a glacial pace. Mr. Pratt fields calls for sequestered wines only a dozen or so times a year, often around graduation and Christmas time. At that rate, the exclusive holdings won’t all be evacuated until sometime in the mid-22nd century. (How’s that for age on a wine?) But his hands are tied. As he states simply, “We don’t own it. We’re obligated to be caretakers.”

In the meantime, the cool, dimly lit, low-ceilinged cellar makes for one-of-a-kind browsing, for both the history buff and the oenophile. Joan Crawford purchased – but never drank – a 1959 Dom Perignon. The same champagne house’s 1976 and 1983 vintages are awaiting Hugh Carey’s uncorking order. Proceeds from “I Dream of Jeannie” bought creator Sidney Sheldon a 1981 Joseph Drouhin Mersault. And who knows what business undertaking netted Ivan Boesky a 1961 magnum of Chateau Mouton-Rothschild.

As for Mr. Nixon, his wine of choice was … King’s Road Villard Blanc, proud product of Asbury, N.J.? Mr. Pratt can’t explain that one, but a 1999 memoir by H. Peter Kriendler (Jack’s brother) states that Frank Sinatra placed a few bottles in the cellar for Nixon’s use. Ol’ Blue Eyes was a Hoboken boy, remember. “I don’t know if that wine was drinkable when it was new,” the sommelier, whose tastes veer toward Riesling and Pinot Noir, said dryly.

The physical cellar itself may be one of the few phenomena of pure good for which we can thank Walter Winchell. Early on, the gossip hound, not popular with Messrs. Kriendler and Berns, was barred from passing the restaurant’s famed iron gate. He retaliated by wondering in print why, of all the gin joints in all of Gotham, “21” had never been raided. Cue the feds, who conducted an 18-hour inspection of the premises. They collected a stockpile of illicit booze, according to Peter Kriendler’s book, though the owners got off on a technicality.

Not wishing to undergo such an ordeal again, the partners called in builder Sol Lustbader to create the most secret of wine cellars. Under an arch in the building’s foundation, he built and seamlessly fit a 5,000-pound brick-and-mortar door activated only when a long metal rod was inserted into a minute hole. Once the rod connected with a mechanism imbedded deep within the door, the portal swung smoothly open, displaying racks of vino.

Also sometimes displayed was New York City mayor “Gentleman” Jimmy Walker. The law and-order-averse Jazz Age pol, a friend of “21,” often escaped with his mistress, showgirl Betty Compton, to his own private booth, which was tucked between the stacks. The booth, since moved to a room under 17 W. 52nd Street, remains as Beau James left it.

The massive door remains the only entrance to the restaurant’s 25,000-bottle wine cellar and has never failed, save for one panicky day years ago, when the lock malfunctioned and the door wouldn’t budge. This briefly made manifest the horrifying notion that gallons of priceless grape might be buried alive. The owners blasted a hole through the wall to the side of the door and sent the eatery’s smallest employee spelunking. After that, no chances were taken, and the block was removed from the lock’s hasp.

Power equipment paid another visit to the wine cellar more recently, when jackhammers lowered the floor at 17 W. 52nd Street by 11 inches. This helped accommodate a long table and several chairs, which daily welcome private wine-oriented lunch and dinner parties. For the price of $110 a person (the lunch tariff) or $485 a person (dinner) one can imbibe within feet of Jimmy Walker’s erstwhile lair and Joan Crawford’s neglected Dom Perignon.

Traffic is good – the room is booked for both meals most days – and that may be good for mobility of the private stock. Perhaps one of those patrons will know where Sammy Davis’s children are keeping themselves. And if they’re thirsty.