The generous D.C. Lottery, which last summer awarded a $100,000 prize instead of the correct $50,000, gave away three new cars yesterday when it meant to hand out only two.

Peter Thornton, a Takoma Park resident, was the beneficiary of the lottery's latest largesse, winning a 1985 Chevrolet Celebrity worth $12,000 when he wasn't even supposed to be entered in yesterday's bonus car sweepstakes.

Douglass W. Gordon, the lottery's acting executive director, said that Thornton will get to keep the car, which cost the lottery $10,800 to purchase.

Last summer, the lottery board decided after several days of discussion to allow an Egyptian man to keep the $100,000 it had mistakenly awarded him in another drawing, twice as much as he was supposed to receive.

"In all fairness to [Thornton] and the integrity of the lottery board, he's entitled to keep the car," Gordon said.

"It may appear that we gave away more than we were supposed to," Gordon said, "but a lot of people will know of the bonus now. It will produce more sales."

Gordon said that the mistake occurred through a clerical error when a letter was prepared, which he signed, notifying Thornton that he was a contestant in yesterday's bonus car drawing.

Gordon said Thornton should have been told that he would be a contestant in a drawing about five weeks from now.

The bonus car sweepstakes is part of the lottery's current Instant Capital game, in which players buy $1 tickets and scratch off the surface of the tickets to determine if they have won cash prizes.

The prizes can range from $2 to as much as $50,000.

Gordon said that over the last several weeks players who have five losing tickets in the game have been eligible to enter the car sweepstakes by mailing in their losing tickets.

He said that the names of 10 players who held losing tickets were drawn over a five-week period and the players were informed that they were eligible for yesterday's drawing, which took place at the G.C. Murphy store at 1214 G St. NW.

But, Gordon said, an 11th letter erroneously was sent to Thornton.

Gordon said that after eight cash prizes and a Chevrolet Cavalier worth about $10,000 were awarded yesterday, officials asked who was the remaining contestant and, accordingly, winner of the top prize, the Chevrolet Celebrity.

Thornton then identified himself, Gordon said.

The name left in the rotating drum, however, turned out not to be Thornton's, but that of Gaster Hunter, a District resident.

Thornton produced Gordon's letter that stated he was a contestant in yesterday's drawing, so Gordon and two lottery board members attending the drawing decided that both Thornton and Hunter would get the Chevrolet Celebrities.

Thornton could not be reached for comment yesterday.

Gordon said he does not know who was responsible for the clerical error, but that he intends to find out. He added that it "depends on the circumstances" whether the employe will be disciplined.