Schulz was interested in very wide ratio designs, even providing for the, very modern, ability to handle a 40 tooth rear sprocket. His derailleur used a pulley cage that, like the 1970s Huret Duopar, had two independent pivot points. This allowed the guide pulley the freedom to more closely track the profile of the freewheel, maintaining an even chain gap. Very cunning.
In this first design the top pivot appears to be unsprung (as it is in the Huret Duopar).