When contractor-horseman Robert Lee Miller Jr. arrived at the Rockville motel where he was shot to death last May, he was carrying with him a $300,000 check with which he hoped to buy control of the corporation he headed.

According to a close business colleague of the dead man, police found the check on the body of Miller, who was president of the construction firm Interstate Brige Co. The check was intended for the purchase of controlling interest in the company, said Dewey Jordan, a business friend of Miller, who, like the slain contractor, owned a construction firm in Frederick, Md.

According to Miller's family and other sources, Miller planned to buy a 50-percent interest in Interstate Bridge, held by ICE Inc., a Nevada holding company.

ICE also owns Excavation Construction Inc., a firm now under scrutiny in two federal grand jury investigations.

Miller was president of Interstate Bridge and owned 37 per cent of the company's stock at the time of his death. Another 13 percent interest in the company is owned by Carl Mason Combs Jr. who founded the company along with Miller. The owners of ICE, which held 50 percent of the stock, are PMI general manager and Excavation Construction president John W. Lyon and Larry A. Campbell, general manager of Excavation Construction.

Shortly before his death Miller had been subpeonaed to testify before a Baltimore federal grand jury inquiring into the activities of Excavation Construction as part of a probe of alleged labor-management racketeering involving the Teamsters Union.

Another grand jury in Washington is investigating the construction firm's relationship with a local judge who suspended thousands of dollars worth of fines levied against Excavation Construction's overweight trucks.

On the day of his death, Miller was at work on a proposal to work as a subcontractor on a construction job in the city of Baltimore, said Jordan. Jordan added that it was unlike Miller to interrupt such work "When he was working on a bid, he just stayed around - all night, if necessary," said Jordan. "He wasn't a person who would neglect a bid."

Jordan said that Miller apparently had told no one why he left. "It had to be something extremely important," he said. "Almost nothing would take him away when he was bidding a big job."

One of the dominating concerns in Miller's life at that point, according to Jordan and other sources, was his desire to gain control of Interstate Bridge.

Miller arrived at the Ramada Inn in Rockville on the day of his death about 6:30 p.m. and checked into a room he reserved earlier that day.

A few minutes later, Miller returned to his silver Lincoln-Continental, where his chauffeur waited, to retrieve his gun and a bottle of whisky.

His body was found about 8:30 p.m. when a room clerk used a passkey to enter Miller's room. Police found $1,900 in cash and a loaded gun on Miller's body, as well as the $300,000 check.

People who knew Miller describe his as a hugh strong and almost fearless man, who would not be easily surprised by an assailant. "Whoever it was [who killed Miller], I'm sure he knew they he was there," said Miller's son Kenneth.

"I don't think any stranger got into his room," said Jordan.

Police have recently focused their investigation of Miller's slaying more closely on Miller's business dealings.

Miller, who lived in an extravagant manner wearing jewelry, buying racehorses and driving fancy cars, left behind an estate that appears to be more debts than assets, according to a paper filed in Frederick County by an attorney representing Miller's estate. Miller's family appears likely to receive relatively little from the dead man's estate.

However, Miller also left behind insurance, including a $2 million corporate insurance policy on Miller's life. That policy was payable to Interstate Bridge and was one of six such policies that covered key officials of the firm. Such policies are a common business practice and usually cover officials who would be difficult to replace immediately.

Miller's stock in Interstate Bridge is currently being held by a Maryland. Bank as collateral on a Loan Miller received before his death. No new president has been chosen for that company.