This is the first of a series of patents for derailleur systems taken out by Ernst Trost of Zurich. It dates from 1935. The fork derailleur sytem described is very much in the tradition of Oscar Egg's Super Champion derailleurs (first patented in 1932). It may be worth noting that Oscar Egg, although based in Paris, originally came from Schlatt, near Wintherthur, about 30 km from Zurich.
It is possible that Ernst Trost went on to manufacture the Versol brand of derailleurs.