Complex sentence: Turret castings, superficial details, and equipment differed between factories; new features were added in the middle of production runs, or retrofitted to older tanks; damaged tanks were rebuilt, sometimes with the addition of newer-model equipment and even new turrets.
Split into simpler sentences: Turret castings, superficial details, and equipment differed between factories. Damaged tanks were rebuilt, sometimes with the addition of newer-model equipment and even new turrets.