Wishing Horse of Oz (c.1935)

This Oz mystery starts in Skampavia where King Skamperoo wishes for a horse using enchanted emerald necklaces. When Chalk, the Wishing Horse of Oz, falls from the sky, Skamperoo decides the emeralds must be from the Emerald City, and decides to conquer all of Oz.

 Market value of this Oz title from various retailers