A 32-year-old Colorado man, convicted of drug distribution following one of the largest single cocaine seizures ever made by D.C. police, was sentenced in U.S. District Court yesterday to five years in prison and fined $5,000.

D.C. narcotics detectives, working undercover, arrested Judah Robert Lyons last March after paying him $133,000 for more than four pounds of cocaine that was 92 percent pure and had a potential street value of $1.5 million.

The prosecution said in court papers that Lyons, a college graduate who has described himself as a horse trainer and part-owner of a Colorado lumber company, told undercover detectives that he could earn$30,000 a month trafficking in cocaine and "that he could not make any money with a degree in Chinese history and art."

Documents seized when Lyons was arrested also showed that he had invested $21,000 in a Texas oil well and had another $21,000 invested in a cash management fund, the court papers filed by the government said.

In addition to the five-year prison term on the drug charge, Judge June L. Green sentenced Lyons to a concurrent term of one year for carrying a weapon during commission of a felony. Lyons, who is free on a $300,000 bond pending appeal, will be eligible for parole in 20 months.

Law enforcement officials said that the investigation that led to Lyons' arrest began in September 1980, when police decided to trace a small, 1/4 gram cocaine sale through a chain of sources to the cocaine dealer.

Lyons, who faced up to 15 years in jail on the charges, had refused the prosecution's offer to reduce the case against him if he would identify his cocaine supplier and testify against two other men he met with in Arlington shortly before he was taken into custody.

The two men, Denny Lee Williamson, 31, of California, and Timothy J. Marfisi, 31, of Florida, were arrested in Arlington by police and federal drug agents, after which police seized another two pounds of cocaine.

Assistant U.S. Attorneys William J. O'Malley Jr. and Joseph F. McSorely, who prosecuted Lyons, said in court papers that the facts of the case made it reasonable to infer that the three men "were members of a lucrative, mobile, highly developed narcotic conspiracy."

The prosecutors noted that Lyons had in his possession a stainless steel, fully loaded .38-caliber revolver and two "speed loaders," a device used to quickly reload a weapon.

"A person who travels interstate packing these items is obviously not coming to Washington, D.C., to merely sightsee or hunt squirrels," the prosecution said in court papers.