Gem Twist had an incredible career at the Grand Prix level.
Along with Gem Twist, horses named Santos and Entrepreneur have been among his champion mounts.
Best continued to ride Gem Twist for several years with great success, including earning two silver medals at the 1988 Olympics in Seoul.
During his career, Gem Twist accumulated more than $800,000 in prize money.
Horse&Hound magazine confirmed the birth and existence of a second clone of Gem Twist.
Best said he never expected his relationship with Gem Twist to carry him to the Olympics.
"He was moderately successful on the circuit, but the luckiest thing that ever happened to him was Gem Twist."
As Gem Twist improved, the prospect loomed that Best, who had no grand prix experience, might be replaced by a more established rider.
The coach still insists that Best without Gem Twist might not be at his profession's pinnacle.
"The ring itself was impressive," said Best, who finished third in the Big Apple on Gem Twist.