This is the original cover painting for the historical novel by Alexander Cordell, a "saga of the men and women who pioneered the great age of railways" - titled, and clearly created for use as cover art, but the source of publication cannot be verified.  Pether produced several cover paintings for Cordell novels published by Sphere in the 1980s - this very likely was one of them, and it's one of the few that's signed and dated - here, 1989.   Painted in gouache and acrylic on illustration board, 11" x 15"  and it also carries a label attesting to its authenticity signed by Pether's widow, mounted to the back.