I've seen this vehicle for the first time in a book that was released before Germany got reunited for the 10th time. There was a Patronenwagen (Ammunition carrier) for the Infantry and the Cavalry. The 'Hauptpark' of the army had more than 80 such vehicles, which must've made them a very common sight.
I personally love the Trittbretter as well as the nice texture of the side-parts.
The wheels are Bavarian from my knowledge since our own Saxon wheels will only turn up on tuesday! :--)