Nothing unusual. Every tank carries a bucket...not only Germany. Sometimes a collapsable canvas, but generally a galvanised iron bucket ... a standard item of issue. Used mainly filled with solvent (or gas) to clean machine guns, tools etc. We generally had them hanging from a lifting eye or tow hook on the rear, sometimes on the rear of the turret, as they tended to get lost running cross country. Maybe the driver had stuff to clean during the course of the work day. Considering his line of work, understandable.