Rosalys Haskell Hall (1914 - ?) was born in New York, and was educated at the Ecole Sevigne, Paris; New Jersey College for Women, and the Ethical Culture Norman Training School. She taught at the Sutton Beekman School in New York, and sold children’s books at the Doubleday Bookshop from 1938 - 1944, after which she worked as an editor in the Children’s Book Department at Longman's, Green & Co.
She wrote several children’s books herself, amongst which is at least one horse-based story, Bertie and Eddie.
Finding the book
Reasonably easy to find, though can vary a bit in price.
Links and sources
Rosalys Haskell Hall’s papers are in the Oregon State University
Thank you to Lisa Catz for the photograph and summary.