This is Zane Grey's Stories of the West Digest 5 - published by Atlas Publications in 1961-1962.
These titles were printed in a smaller size (175x134mm) compared to the original Dell title.
64 pages, glossy colour cover, black-and-white interior.
Cover of Zane Grey's Stories of the West Digest 5 and Dell's original
cover of Four Colour 632 Zane Grey's Fighting Caravans (1955):