Four years ago, Michael Hunter found Scrimshaw, a 10-year-old gray gelding that won today's $4,500 first prize in the Upperville Jumper Classic, wandering in a field in Bucks County, Pa.

"The guy I bought him from was an artist who had a hack stable, and was using him as a field hunter," Hunter recalled. "He kept asking me to come and look at him and I didn't. Finally I went to see him.

"I rode him over some tree limbs and piled some tires and cans to jump over. I thought he'd be a good jumper."

His hunch, paid off again today as 6,200 persons gathered on a hillside nestled in the Blue Ridge Mountains for tailgate pienics and the pleasant diversion of watching 24 horses compete in the final $15,000 Jumper Classic of the 124th Upperville Colt and Horse Show.

Attired in scariet, navy blue or forest green jackets and velvet caps, 13 riders guided their horses over 1 gates, oxers, liverpools, posts and rails and walls reaching up to 5 1/2 feet.

Only 11 horses completet the course without jumping or time faults to qualify for the second round jump-off. The number of obstacles was reduced to eight and the fastest time in completing the course determined the winner.

"I galloped right to the first fence. That's where I won it today," Hunter said. "If you get off to a good start, you can usually a good three-second edge."

Scrimshaw, which won the Palm Beach and the Madison Square Garden Grand Prix last year, finished the second round in 39.542 seconds to win the classic and the blanket of yellow roses.

The Jones Boy, riden by Katie Monahan, placed second with 41,101 seconds for $3,300; The Cardinal, ridden by Olympian Buddy Brown followed (41.585) for $2,250; Singapore, with Terry Rudd, was fourth ($42.467), $1,500.

Fifth was Viscount, riden by Brown (43.223), $1,050; sixth, Do-Right, Dennis Murphy (42.246), $900; seventh, Idle Dice, Rodney Jnkins (42.843), $750, and eighth, Balbuco, Conrad Homfield, (43.95), $750.

The last three horses had four faults each.

Scrimshaw was purchased four weeks after Hunter bought him "for top dollar" by Edwin W. Orr, who was advised by a friend: "Don't try 'im, buy 'im," Hunter said.

Hunter continued to ride Scrimshaw for Orr. "When he won his first class, I couldn't believe it," Hunter said. "I jsut said, 'It's the Great White.'" The nickname has stuck to the silver-gray former field horse.