Who is the mystery horse under house arrest in barn 59 at Belmont Park?

At Belmont they know this much about the captive steed they're holding under close 24-hour guard: He won the ninth race on Sept. 23 at a stunning $116 mutuel under the given name of Lebon.

Ay, there's the rub. It is strongly suspected sombody gave the horse a name that wasn't his.Belmont's players were duped. They had bet in good faith against No. 2, a certified cheap one they didn't like each at odds of 57 to 1. One man at the track pulled off a $78,000 killing at the $50 window. And now the officials of the nation's must prestigious race track are wretched at apparently having been bunkoed by the slick switch of the a fast horse for a slow one, a classic ringer case.

They have some suspects, and an improbable trail that begins in far away Uruguay and leads to the town dump in Muttontown. Long Island, and to barn 59, where Belmont's handsome, innocent prisoner, whose only sin was to run as fast as he could on Sept. 23, cannot speak for himself.

It was in Uruguay in May that a batch of South American horse.

Lebon among them was brought by an group for shipment to New York. It was in Muttontown in June that the keepers of the town dump received a horse carcass for burial, with a proper veterinary's certificate saving the deceased was Cinzano, a respected South American stakes winner which had had the misfortune to break his skull in a stall accident, it is said shortly after arriving from Uruguay.

The vet said he had to put him away, a track euphemism for destroying a horse. Lloyds of London, which paid off $150,000 insurance policy on Cinzano, now wants its money back.

Now to barn 59 where the Belmont people and others suspect that Lebon is Cinzano reincarnate. They think the lively winner on Sept. 23 was not the mediocre Lebon but the speedier shipmate from Uruguay. They suspect an interchange.Both had some similar markings.

The Belmont people are infuriated. So is the New York Jockey Club which is supposed to guard against such trickery with its horse-identification apparatus. So is the New York Racing and Wagering Board. Whose offtrack customers also may have been duped. So is Nassau County, which suspects that something bad has happened on its turf, and like the others, has called for hearings starting Monday.

All want to talk to Dr. Mark Gerald, the veterinarian who says has been suspended by the New York Wagering and Racing Board for "possible racing fraud." Grerald not only denies all guilt, but has confused the whole situation by saving he was the bettor who won the $78,000 on "Lebon."

Bettors who have made a big haul on a race being probed do not characteristically volunteer suchinformation.

There would have been no furor at all, no suspicion of tricks, were it not for the sharp-eyed racing fans in Montevideo. Uruguay, whose newspaper showed them a wire photo of "Lebon" in the winner's circle at Belmont. Local pride was quickly replaced by disbelief. The horse they were looking at was known to them not as Lebon, the mediocre one, but as Cinzano, the good one, they said.

"Something is rotten in America." was their reaction, and the news reached Belmont.

That the Jockey Club and its identification troops did not distinguish themselves is apparent. Extra precautions were necessary because South American horses do not bear the lip tatoo with which all U.S. horses are marked early in their life. This happens before their first start, and usually after they have passed their suckling or "on the mother" phase. South American horses come to the U.S. bearing merely a full certificate with a description of markings.

Larry Adams, the jockey who got "Lebon" home four lengths in front, said it was a "pleasant surprise" to him. "I thought he was just a horse who woke on grass."

If the recognition of a news print photo in Uruguay that "Lebon" wasn't Lebon, but Cinzano, was so speedy and emphatic, apparently the two horses were not even good look-alikes.

If Peter Christian Barrie was still alive, anybody interested in switching the two horses may well have gotten away with it. Barrie is the Englishman who was recognized as the "Rembrandt of the race tracks." He would have done a job on the long white blaze on Cinzano's head that enabled Uruguayians to compare him with the shorter white star on Lebon.

If George Bellows, who had a fondness for doing boxing canvases, has been acclaimed as the finest painter of the American sporting scene, Barrie has been recognized in certain circles as an artist of at least equal talents. Barrie scorned canvas. He worked on horsehides, and so artistically he was ruled off every track in the United States and finally deported to his native England. He worked from life on life, painting good horses to resemble bad horses so they could go to the post at long odds.

The ulimate job was the one the rascally Barrie did in 1931 for Nate Raymond, the gambler who held a hand in Arnold Rothstein's last card game.For Raymond he used his dyes and paint brush to make a speed horse. Akhnatom, look like Shem, a slow one. In addition to transposing Shem's markings on Akhnatom. Barrie's final artistty was to disguise the imposter. Akhnatom, as a gelding, which was the sex of Shem. He did this by concocting his own solution for "freezing" the testicles to the point they virtually disappeared.

The hoax worked in the first race at Havre de Grace. As Shem, Akhnatom won a $14 mutuel. So joyed were they with the money they plundered from the mutuel machines and the unsuspecting bookies, the Raymond-Barrie gand didn't even bother to pick up the purse money.

One of the items bothering the probers at Belmont, which would have taken care of, is the three-inch scar on the left shoulder of "Lebon" the Sept. 23 winner. This was duly mentioned in the Jockey Club's identification chart for the horse. But sources have told the Jockey club the real Lebon didn't have any scar on his shoulder.

Five weeks after the race, the New York officials are now in a tizy to do something about it. On Wednesday they dispatched a five-man investigative team to Uruguay to track down the sires of Lebon and Cinzano and take blood tests that might establish the paternity of the suspected ringer.

But while they were still in flight the task of New York's doughty task force was virtually aborted. To New York came world that the respective sires of Lebon and Cinzano. Lemmy and Tudor Park, were no longer alive in Uruguay or anywhere else. Lemmy has been dead for two years. Both stallions were 9 years old, relatively young for breeding sires to come to the end of their time, and there are now suspicions of foul play at the Uruguayan end of the game.