Jo Ann Argyris, seen Friday at the Railroad Pass where she won a jackpot a day earlier, had to be prompted that she had hit another million-dollar jackpot. Photo by Gary Thompson.

After winning a $1 million slot machine jackpot less than a year ago, one would think Jo Ann Argyris would easily recognize the symbols that signify a large cash prize.

On Thursday night the Boulder City resident hit her second $1 million jackpot in a span of less than a year. But once again, she had to be told she was a big winner.

"My daughter looked over at the machine, and said, 'Mom, you did it again,'" said Argyris, a self-employed single mother of two and grandmother of three. "When I realized it, I just put my head on her shoulder and cried."

In June at the Sunset Station, Argyris won the $1 million top prize on a penny-based, four-level progressive video slot machine, dubbed Millioni$er, that is distributed by Australia-based Aristocrat Technologies.

She was playing the same type of machine again, this time at the small Railroad Pass, when she struck the $1 million jackpot.

"I saw the symbols, but it just didn't seem possible," said Argyris.

The odds of the same person hitting two $1 million jackpots on the same type of machine in a year's time are astronomical, several gambling experts said.

"That is fricken' amazing," said Anthony Curtis, president of Las Vegas Advisor.com. "You're looking at odds in either the billions or trillions. I don't think I've ever heard of somebody doing something like that. The Aristocrat game is popular, but it hasn't hit all that often. For this woman to do this twice is a pretty amazing accomplishment."

University of Nevada, Las Vegas professor Bill Thompson, who specializes in gaming issues, called Argyris, "one very lucky lady."

He said it would be "mind-boggling" to come up with the odds of that particular occurrence.

"Of course, I wonder why someone who has hit a $1 million jackpot would feel the need to go out and try again," Thompson said.

The $1 million jackpot is part of the Aristocrat machine's secondary bonus system that is triggered randomly during play.

Argyris had been playing for 10 minutes and wagered about $35 when the jackpot hit. According to Aristocrat, the $1 million prize requires a $2 wager.

"It's kind of unusual. We don't get a lot of million-dollar winners here," Railroad Pass general manager Mike Poehling said of the locals-oriented casino with 350 slot machines.

Argyris, who said she actually favors video poker, frequents different Henderson-area casinos a few nights a week.

"I told everyone last year I'd win it again," Argyris said. "I didn't think it would happen this quickly."

Aristocrat, which shares in the game's revenues with the casino, is responsible for paying the jackpot.

After two $1 million jackpots, Argyris still can't be classified a millionaire.

Nevada gaming regulations allow the prize to be awarded in installments -- $50,000 annually for 20 years. However, as she did last year, Argyris accepted a lump-sum discounted payment for the jackpot -- a little more than $400,000 after taxes and fees.

Last year, she used the winnings to pay off her mortgage, remodel her house and take 10 family members on a vacation cruise to the Mexican Riviera.

By Friday, Argyris said her grandson was already planning this year's trip.

"He immediately wanted to know where we going," she said. "I'm thinking Hawaii."