I feel like I'm cheating, but I need this point to go over 52. The name E/V-4 applied to models 1917 and 1918. If it's not this, than it should be Model 1915, having the same origin as Erhardt BAK (baloon shooting car).
Yeah, that's it.
But it looks so much like Schupo-Sonderwagen/21, which is a derivative of SDkfz3 (Daimler)!