Kaelble?
It was identified as 1953 Kaelble Thermoswagen
I've found the puzzle picture among other in a truck forum. They said:
"The photo shows a truck with box body from the Bremen forwarding company Joh. Bischoff. At first I thought I could see the Kaelble emblem on the radiator grille, but on closer inspection I noticed that it was a Bischoff lettering. However, the similarity of the two lettering is striking, could it therefore possibly be a Kaelble?
By the way, the photo was taken on 03.06.1958 on the Himmelsleiter in the Rhön"
Then someone answered:
"Yes, you are absolutely right, it is a three-axle Kaelble Thermoswagen, probably KD 631, from the beginning of the fifties, until 1953 with 150 hp engine and then with 180 hp engine. This magnificent truck had a heavy 24t. three-axle trailer in tow. For better illustration despite poor quality, two pictures from my archive of this unique vehicle."