Any ideas, I'm guess about 1940
I think it's not determinable. There is no such troop unit sign or tactical sign of the Wehrmacht, also not for this special Sd.Kfz. 221. There is no such abbreviation in the official information office about the Wehrmacht, either.
That's why most likely it's a sign of barracks this vehicle came from, or a sign of the responsible soldier or something. Anyway it seems it's not an official abbreviation. Maybe it abbreviates the town or village where they are coming from, but one does not have a fast clue which one this could be.
I also searched Google Pictures for photographs of that Panzerspähwagen but all available vehicles of this type don't have a similar sign, especially at this place on the tank.