hi cave dweller, during ww2 old or damaged tanks were used as towing or repair vehicles, you would need a tank to tow a tank especially over rough ground. the box on the top was used on the panzer iii chassis to basically create a mobile workshop, obviously after the turret was removed. the box wasn't actually used on the panzer iv that i am building but i thought it would look cool to use the idea!
the disc camo pattern was a real pattern used later in the war, it must have taken some applying to a full size tank, it sure did on the model!
thanks for your interest my friend