"The day before I was scheduled to get on a plane and come here," she said behind the 18th green of the Dinah Shore Course at Mission Hills Country Club after her second round, "I didn't have an arm." If that sounds alarming, it's because her left arm is a prosthetic device she was fitted for following cancer surgery nine years ago. The prosthesis attaches by suction, but occasionally it starts to "leak," or give way, which is not a reassuring thought on a follow-through.

Cooper, a new Floridian with her husband, Harris, and 11 year-old daughter, Nicole, was first diagnosed with cancer in 1978. Nine years later, in February 1987, doctors amputated the arm above the elbow.

The surgery affected her golf game, but not how you might think. The lowest Handicap Index she had before surgery was 4; afterward she had it as low as 1. (She entered the Women's Mid-Amateur with a 1.7.) "When I play I see myself playing with two arms," she says. "That's the way I learned."

Her play has improved in each of the three Women's Mid-Amateurs in which she's competed. Two years ago she was back in the pack following the 36 holes of stroke play, and last year she got into a seven-for-four playoff for the final match-play berths. (She was one of the three who missed.) At Mission Hills she followed an opening-round 82 with a 78 that was good enough to make match play, but in the first round she was eliminated by Cindy Carroll of McKinney, Texas, 3 and 2.

"I thought she played great," said Gail Flanagan, a member of the same group with Cooper for the two days of stroke play. "She could handle any kind of shot, any kind of lie, and she's a smart player. She's got very good course management.

"I didn't expect her to hit the ball as far as she did, as well as she did, but she hit it out there as far as a lot of players." Certain shots are more troublesome for Cooper. "I don't like the ball above my feet," she explained. "I have a few things I can choke down on, but if I have to get to the end of the grip I can't do it." The end of her prosthesis is fitted with a locking clasp, which accommodates the thicker end of the grip well but doesn't adjust as she moves down the tapered end of the grip toward the shaft.

She points to work with instructor Mike Calbot as instrumental in her effort to play again following the surgery. "Since I don't have the hands to make that little flick at the end of the swing," she notes, "I have to have good technique. Id tell him something like, `I don't have the angle I used to,' and he'd tell me, `That's one less thing you have to worry about."

But it's certainly not as severe as preparing for a national championship with one less arm than most people would think they need.