Before he went Hollywood, the thoroughbred gelding Finders Key accounted for only torn-up mutuel tickets at Los Alamitos Race Course, a track better known for quarter horse racing in Orange County, Calif. Winless in four $2,500 claiming races, he was beaten by a combined 30 lengths, never finishing higher than fifth.

His former trainer from Los Alamitos, Curly Ortiz, said recently that Finders Key, despite aristocratic breeding, “was not a gem in any sense.”

He also did not think the horse could become a movie star, but Finders Key proved him wrong.

Finders Key raced as a 3-year-old in 2002, when he was owned by Vincent Timphony and his wife, Scarlet. Timphony was a little-known trainer and Wild Again was a long shot in 1984 when they combined to win the first running of the Breeders’ Cup Classic.

Timphony, who never had another horse as good as Wild Again, died in 2010.

“Horses are like people,” Scarlet Timphony said. “You can’t tell what’s inside by just looking at them. We had a horse named Fasternhel, who was well-bred, but he hardly lived up to his name. We sold him for $1,200, and he became one of the top polo ponies on the international circuit. So there we were, trying to force Finders Key to race, when what he wanted to do was be in the movies.”

Running before crowds that barely topped 1,000 at Los Alamitos, Finders Key now has a page on Facebook and has attracted international attention.

He was discovered by Rusty Hendrickson, the wrangler for “Seabiscuit,” the film about the Depression-era racehorse in which he made his screen debut in 2003. Finders Key was one of 10 horses who played Seabiscuit; two years later he was seen in “The Legend of Zorro,” and now, billed as Finder, he is the lead among the 14 horses portraying Joey in Steven Spielberg’s “War Horse.”

The movie, set in World War I, turns on a young soldier’s devotion to his horse. Finders Key is so versatile that in an early scene, in an inventive twist, he plays his own dam giving birth to Joey.

The movie, nominated Tuesday for an Oscar for best picture, used almost 300 horses for one battle scene. The best acting was by Finders Key, observed Alex Brown, a veteran exercise rider, who wrote a book about Barbaro, the 2006 Kentucky Derby winner. “Often in horse movies, as a horseman, you cringe at a couple of scenes because they are either unrealistic or simply incorrect,” Brown wrote in Steeplechase Times. He added, “In ‘War Horse,’ Joey’s role was brilliant.”

“He’s just right for some of the things they want to do,” said Ortiz, who saw “War Horse” the day after Christmas. “They’ve trained him into becoming a very good trick horse. That thing he did in the first part of ‘Seabiscuit’ was really terrific.”

In “Seabiscuit,” Chris Cooper, playing the trainer Tom Smith, is introducing his new horse to a cocksure jockey at the barn at Saratoga. Finders Key, playing a young Seabiscuit, rears up despite being restrained by two handlers with ropes. The jockey backs off, but the horse lunges toward him and rips his shirt. The jockey backs off, muttering a profanity. “He’s nuts,” he adds.

Coincidentally, the jockey was played by Kevin Mangold, who rode Finders Key in his final race, on Aug. 8, 2002, at Los Alamitos. Mangold, who retired from riding in 2006 after winning 52 races over six years, has appeared in several film and television productions as an actor and stunt rider.

Mangold and Scarlet Timphony said they each saw “War Horse,” but neither knew Finders Key was in the film until a reporter told them.

“I cried my eyes out during that picture,” Mangold said. “I’m kicking myself for not recognizing him. I’d say that our acting careers have turned out much better than our racing careers.”