GGrrrrrrr! I have several books on my shelf with pictures and detailed descriptions of Henschel steam commercial vehicles. But unfortunately the penny didn't drop.
Sometimes you can't see the wood for the trees.
Here some additional informations:
As a manufacturer of locomotives, Henschel had a great deal of experience with steam engines, but only with coal firing. For road vehicles, however, liquid fuels were in demand. For the sake of simplicity, a licence was obtained from Doble Steam Motor (USA), using liquid fuels (petrol or diesel). However, Doble only built drives for passenger cars; these had to be optimised for commercial vehicles (Using tar oil, larger heating surface, automatic feed of fuel and water, Reduction of water consumption). To assist with the modifications, the Doble brothers visited Henschel in Kassel several times. Several trucks (including 10 for the railway) and six buses were built. The first three buses (e.g. for Wuppertal and Dresden, see photo) had a bonnet. They were preferably used on mountain tracks and proved themselves excellently there (high starting torque, no clutch wear, good heating). There were also three front steerers with the boiler system at the rear and with a condenser fitted at the front. Two for Bielefeld and Kassel with the body of the puzzle bus and one for Bremen (see photo). Due to the naval build-up, the demand for tar-oil rose rapidly, and so did the price. Commercial vehicles with steam engines were no longer profitable. The Bremen bus was therefore given a diesel engine, and in 1943 it was converted to city gas. The Bielfeld bus was equipped with a Deutz diesel engine as late as 1950.
