The aim of Mr. Stern was to invent a machine with the least likelihood of leakage and to lower manufacture costs by simplifying the assembly of the pieces.
The result is to found in this patent n°179621 granted in 1954.
Another smart thing was to bring the heat source right under the water tank, and the pressure increasing system directly in the water tank.
The result: a all-in-one head standing on a hollow foot... but is the foot necessary? NO! Mr. Stern mentions the possibility to fix just the head on the wall!
On the picture above, the piece n°7 is a electrical heating source which could be screwed to the body of the machine. Another possibility was to use spirit, in this case, the space had to be made bigger to allow the flame to heat the water tank properly.