National Velvet has been through a goodly number of reprintings. Below are the examples I have been able to find so far. Many thanks to Susan Bourgeau for providing photographs of the American versions.
Enid Bagnold, adapted by Lee Wyndham
ill Al Brule
Grosset & Dunlap 1961
Susan Bourgeau, who sent me the pictures of this version (illustrated above), said: “This is a picture-book sized abridged/adapted version....frankly, it's terrible, but I bought it because a) it was a dollar, b) the illustrations were such fun 50s/early 60s kitsch, and c) it kept it out of the hands of anyone who might think it had anything to do with the real book as Bagnold wrote it!
Wyndham was actually an author in her own right, and is best known for the Suzie ballet books (what is it with horse book/ballet book authors?), written for a much younger reader than Lorna Hill's books. The hardest to find of them is Suzie and the Ballet Horse, in which Suzie dances with a Lipizzaner!
Wm Morrow ,1949
ill Paul Brown
USA 1st edition
Illus Laurian Jones
Heinemann Vanguard Library 1953
Jacket design Edward Bawden
Early UK Heinemann printing, illus Laurian Jones
(US movie tie in)
Triangle Books 1945
cover art is photo collage from movie w/Elizabeth Taylor, Mickey Rooney
internal illustrations by Laurian Jones
Little Golden Book
Golden Press 1961
story by Kathryn Hitte
illustrations by Mel Crawford
Has little to do with original book. Based on US television show - horse renamed King.