Correct, this car used the W 23 S chassis with rigid axles.
What makes the puzzle picture really interesting is the fact that (according to Erdmann/Westermann's Wanderer book) just one single Farmerwagen prototype was built in 1941. The puzzle picture was taken after WW2 when the car was owned by the bus company Deist & Trube in Bad Sooden-Allendorf. The cellophane side and rear windows had been replaced by solid wood then and a wood gas generator had been added.