A 23-year-old student at Virginia Polytechnic Institute and State University with $10.08 in his checking account has been identified as the mystery lobbyist who last weekend sent $200 checks to members of the Virginia state senate accompanied by appeals to raise the state's beer drinking age to 21.

Ronald S. Moore, a third-year finance major at the Blacksburg school, has acknowledged to state police that he made the mailing, which purported to represent the views of "marijuana businessmen" on the drinking age issue, law enforcement authorities said today.

Moore is now under investigation for attempted bribery and possible other violations by Richmond Commonwealth's Attorney Aubrey M. Davis. There was, however, confusion among authorities today about how seriously to take the matter.

When contacted by state police, Moore was "polite and very cooperative" and thanked them for their investigation, law enforcement sources said today. "This is the first time I've ever had a case like this in 11 years," said Davis.

Each senator who received one of Moore's letters also got a check made out to a different senator--an apparent attempt to avoid bad check and bribery laws. And as some senators had correctly surmised, Moore was apparently practicing "reverse psychology"--urging senators to vote for the higher drinking age bill, which has already passed the House of Delegates, when he really wanted it defeated.

"Marijuana Businessmen presently have to compete with beer on unfair terms," read the letter. "Marijuana is illegal, cannot be advertised and cannot be distributed easily . . . with the new 21 law, marijuana businessmen will be able to compete fairly in a major market (18-20.)"

In fact, Moore told the Roanoke Times & World-News that his real purpose was to warn the senators that there would be increased drug use among teen-agers if the drinking age were raised. "I was just worried about people of a younger age," Moore said.

"I guess I had a lot less effect than I thought I might," Moore also said.

Some senators interviewed today said they had followed the request of the state attorney general's office and turned their checks in for use in the investigation. However, Sen. Wiley F. Mitchell (R-Alexandria) protested that he could not because Sen. Willard J. Moody (D-Portsmouth), who received the check made out to Mitchell, had torn it up. "I thought that was downright impolite," Mitchell said.

Meanwhile, at least one of those senators who did not receive a check claimed he was indignant. Said Fairfax Democratic Sen. Richard L. Saslaw, "I feel discriminated against." CAPTION: Picture, RONALD D. MOORE . . . $10.08 in his checking account