That was an appealing note to the sale of the New York Mets the other day for $21 million -- the identity of the man who bought them.

He is, surprise, the great-grandnephew of Abner Doubleday, from whose inventive mind the game of baseball sprang full blown in 1839 on a spring daya in Cooperstown, N.Y., according to legend. The new owner is Nelson Doubleday, of the noted book family. Who cares if the fame of his celebrated ancestor was spawned by one of the most outrageous lies ever visited on the American people? It is now a truth that a living Doubleday, active and eager, is an important part of baseball. Nobody ever thought it would come to this.

The price of $21 million for the Mets is almost as astonishing as the reentry of the name of Doubleday into the game, 140 years after Uncle Abner supposedly laid out the first baseball diamond with a stock on that dusty field in upstate New York.

Of all the teams in the National League to attract a purchase at that record price, the Mets were the least likely. They were dead last in their division last season, and the year before that. The modern Mets have been reviving the lament of their late manager, Casey Stengel, who once asked, "Can't anybody here play this game?"

They had a home attendance of 788,000 last season, so fallen from favor that nearly 2 million Met fans who helped them to a record crowd of 2,697,000 10 years before, stayed away from their games. The team's prospects for 1980 are viewed as no better.

Edward Benenett Williams is now looking like a genius in the market place for his coup of acquiring the Orioles for a paltry $12 million. He bought a team that drew 1.7 million last season -- more than double the Mets' attendance. The Orioles were a pennant winner, came within one game of winning the World Series and even now may be verging on a dynasty.

One explanatory item is the difference in local television revenues. The Mets count theirs in millions, in the No. 1 TV market, but the Orioles in thousands. Even that factor does not account for the huge spread in their purchase prices.

Last season, across town in New York the Yankees drew 2 million more fans than the Mets, making George Steinbrenner's purchase of them for $10 million from CBS in 1973 a stunning steal. It seems that everybody except CBS made money from the Yankees. They paid Del Webb and Dan Topping $13.2 million for the club in 1965 and eight years later sold it to Steinbrenner for $3.2 million less.

Six years after Webb and Topping bought the Yankees from the Jacob Ruppert estate for a mere $2,875,000 in 1945, they sold Yankee Stadium to investors for $6.5 million, keping possessionof the franchise and the league's best players.

So much for the fiscal background of Mr. Nelson Doubleday's entry into baseball.

His great-granduncle, Abner, won legitimate recognition as the Union Army major who ordered the first cannon fire at Fort Sumter in reply to the Confederate attack. He became a major general, did honor to that rank, and in 1893 was laid to rest in Arlington National Cemetery, without any references to any connection with baseball.

His recognition as the father of baseballl is a preposterous myth perpetuated by the lords of the game to give it some kind of a romantic figure and a nice place to erect its Hall of Fame, even if it was on a fanciful notion that Doubleday as the game's creator.

The evidence against Doubleday as the inventor of baseball is pretty damning. It wasn't until 14 years after his death that his name was even mentioned in connection with baseball. His 350-word obituary in the New York Times made no reference to any interest in the game.

A prolific writer himself, Doubleday never mentioned baseball in any of his works. And, in later years, a foray by researchers into the archives at West Point produced a report of the Association of Graduates that said of Doubleday, "He was a man who did not care for or go into any outdoor sports." d

How then, was bestowed on Abner Doubleday the considerable honor of progenitor of America's game? The whole thing stemmed from a feud between A.G. Spalding one of the first great names in baseball, who later gave his name to sporting goods, and Henry Chadwick, famed as the man who gave baseball its scoring system.

Chadwick, British born, was saying loudly in that era that baseball was derived from the English game of rounders, which also was played with bat, ball and bases. He credited Alexander J. Cartwright with refining rounders and organizing it into America's game for the New York Knickbockers in 1845, and declared Cartwright should be recognized as baseball's founder.

The offended patriot Spalding, who replied to Chadwick's claim by submitting a flag-waving brief in support of its American origins. That Spalding was something less than objective was seen in his declaration, "The tea episode in Boston Harbor, and later our fracas with England in 1812 had not been sufficiently forgotten in 1840 for anyone to be deluded into the idea our national prejudices would permit us to look with favor, much less adopt, any sport or game with an English flavor."

At Spalding's suggestion, a special baseball commission was appointed in 1906 with instructions to delve into the antiquities of the game -- alll this reported in the excellent "History of Baseball" by Joe Reichler and Allison Danzig. The committee's recommendation a year later was that Doubleday had started it all.

Doubleday's name came into the search for a founder because, Spalding said, a mining engineer in Colorado, one Abner Graves, had written him a letter saying he could testify that Cooperstown was the birthplace of baseball. Graves said he was "a fellow pupil at Green's Select School in Cooperstown in 1839" when schoolmate Doubleday first laid out a field with his stick in the dust and described the location of the players.

Later, this proved to be false, because in 1839, no matter what Abner Graves said, Abner Doubleday was then a cadet at West Point, not a pupil at Green's Select School.This was only one of the truths about Doubleday disclosed by Robert William Henderson, chief supervisor of the New York Public Library reading room, who made a lengthy project of pointing the creation of baseball twoard Alexandrer J. Cartwright, not Abner Doubleday.

There could even be some doubt about the claims of both the Doubleday and Cartwright camps. Before he died, a reputable witness testified that he was playing baseball at Harvard in 1829. This was Dr. Oliver Wendell Holmes. But no matter, it's nice to have a Doubleday in the game, at last.