Who built this, what was it based upon, and why was it built?
1937/38 Mercedes Benz advertising semi trailer truck built by Gaubschat for Kienzle watch and clock company. Two made, this one is number 2.
One point to Hiawatha for the complete answer.
Because this vehicle was mentioned in another puzzle, I figured it should be included. When I discovered that vehicle #2 had very few pictures online, I decided it should be the subject of my puzzle.
Original image:
Even two beds and a bathroom for the personnel were included.