Minecraft wiki entry for Chestplate, associated text: Zombies and skeletons have a small chance to spawn wearing any armor. There is an 8.5% chance (9.5% with Looting I, 10.5% with Looting II and 11.5% with Looting III) for the mob to drop a chestplate upon death. The chestplate the mob drops is usually badly damaged, and rarely enchanted.