One of the biggest winners in Maryland's slot machine sweepstakes could be a little-known Indiana gambling firm that was founded by a farmer and a former trucking executive and until recently had only 10 employees.

Centaur Inc., a privately held corporation based in Indianapolis, was betting that slots would come to Maryland when it agreed in October to pay $55 million for Rosecroft Raceway, a Prince George's County harness track on the verge of shutting down.

The company was formed 10 years ago and has invested in a Midwest riverboat gambling venture, a California casino owned by a one-member Indian tribe, a restaurant in Times Square and a small casino in Colorado. Centaur also holds a minority share in the Hoosier Park harness track in Indiana, but it has never owned or operated a racetrack by itself.

Centaur's modest gambling portfolio would expand exponentially if the Maryland General Assembly approves slots at four racetracks, including Rosecroft. The Oxon Hill track would offer 3,500 slots under a plan approved by the Senate -- 10 times as many as Centaur's tribal casino near Palm Springs, Calif.

Studies commissioned by the gambling industry show that Rosecroft would be the most profitable of the tracks if slots are approved. Its advantages: easy access to the Capital Beltway and proximity to Washington and Northern Virginia.

"That'll be a gold mine if it happens, no doubt about it," said Eugene Christiansen, head of a New York gambling research and consulting firm.

But as lawmakers weigh a plan that could give Centaur a 15-year license to gamble, few have studied the firm's record, including troubles with regulators and tax officials.

"If we're going to in effect marry these people for the next 15 years, we better make sure we know damn well who they are," said W. Minor Carter, lobbyist for a coalition of anti-slots groups. " . . . Centaur is the poster boy of this. They are the new kid on the block, and they're going to get the prize in this, but we don't even know who they are."

Although it keeps a low profile, Centaur has a history of spending heavily on political contributions and lobbyists. In Indiana, it spent more than $800,000 in lobbying fees over two years in a failed attempt to legalize slots at its track there.

More recently, the firm's investors donated $120,000 last year to political committees affiliated with soon-to-be Pennsylvania governor Edward G. Rendell (D) in an effort to obtain a license to operate a racetrack and slots near Pittsburgh. They also donated $112,000 to federal political campaigns in 2002. In Maryland, they gave $3,000 to Republican Robert L. Ehrlich Jr.'s successful campaign for governor.

The company has run afoul of regulators in Indiana on two occasions, resulting in a $500,000 fine and other penalties, records show.

Centaur shareholders are also mired in a tax dispute with Indiana officials and could be liable for more than $800,000 in unpaid income taxes and penalties, according to papers the firm filed in Pennsylvania.

Centaur has emerged as a powerful player in Maryland's debate over slots, even though it doesn't actually own a racetrack yet.

The firm signed an agreement in October to buy Rosecroft from the Cloverleaf Standardbred Owners Association, a local group of horse owners and trainers that had purchased the track in 1995. The sale has not been finalized. It first must be approved by the Maryland Racing Commission, which has received only a partial application from Centaur.

Company officials said the deal is on hold until the assembly takes action on slots. They added that they are committed to buying the track even if slots are not approved.

"We think we can bring some real opportunities to grow the business, with or without slots," said Jeffrey M. Smith, Centaur's president and chief executive for racing. "We can improve the racing product and the picture at Rosecroft, but I don't want to mislead you. We can't restore Maryland standardbred racing to its former prominence without help."

At the same time, the firm has argued that slots would be no windfall. Centaur executive John McLaughlin has told lawmakers that the company stands to earn $7 million a year or less if the Senate bill becomes law.

Anti-slots lawmakers questioned why Centaur would push so hard for slots if there was no money in the deal. "That says to me that they're being untruthful and disingenuous," said Sen. Paul G. Pinsky (D-Prince George's). "It's probably the most lucrative market. I think they're low-balling it for their own purposes."

Others have their doubts about whether Centaur intends to keep the track. "None of us really know anything about Centaur," said House Speaker Michael E. Busch (D-Anne Arundel), the leading obstacle to slots in the assembly. "They certainly don't have any roots in Maryland. It's not too far-fetched to think they'd sell out after getting slots. . . . They could make a deal with someone else and turn a quick profit."

Centaur has mounted an energetic lobbying campaign in Annapolis, relying on three top executives and a half-dozen lobbyists to press its case. At the same time, it has steadfastly avoided publicity.

Partly because it is a small company, Centaur is relatively unknown on Wall Street, even among gambling industry analysts. The firm operates out of an office suite in downtown Indianapolis, where it has 10 employees. It employs 300 at its recently acquired casino near Denver.

"We're a private company," Smith said. "Principally because our initial projects were as minority partners, there was no real desire or need to market ourselves to the public."

Records filed with the Maryland Racing Commission indicate that Centaur's primary investors in Rosecroft would be its chairman, Roderick J. Ratcliff, and vice chairman, R. Michael O'Malley. They and their families would own 72.5 percent of the venture.

The two are agribusiness executives from West Lafayette, Ind. Ratcliff is a former trucking executive and fertilizer salesman; O'Malley a corn farmer and developer.

Since its formation in 1993, Centaur has been punished twice by Indiana regulators.

In February 2001, the Indiana Gaming Commission fined Centaur $500,000 for improperly using its riverboat casino license as collateral for a letter of credit.

Three months earlier, Centaur was penalized by the Indiana Horse Racing Commission for failing to disclose that it had sold purchase options in Hoosier Park to two lobbyists. No fine was imposed.

Centaur has characterized the violations as unintentional mistakes.

"They were a young company," said Smith, who joined the firm two years ago. " . . . They had very limited experience dealing with regulatory matters."

Staff researcher Bobbye Pratt contributed to this report.