Another Umbau-wagen?

[Hanno Spoelstra]

See the picture below for another curious German conversion of a car of unknown make to me. Not sure if this is a Umbau-Wagen conversion, or a one-off. It seems like they grafted a locker on the rear to come up with a makeshift Kfz.11 m.Pkw.(o) 4x2 (medium car) or Kfz. 15 Nachrichten Kw. (signals car). Typically, the rear locker was a feature of the Kfz. 15, but in that case it should have cable reel holders on the front mudguards as well.

Who can identify the make/type of car? (David, Bill?) Was it a captured Allied vehicle?

Thanks,
Hanno

Note: the full picture can be found at Akira Takiguchi's Wehrmacht in World War II website. Caption: "This one is marked Betr.Tr.a.2 (Betriebstrupp a - telephone operations section). Three-color unidentified Armeekorps(?) marking is clearly seen."