This is the second of two patents covering Claudius Blanchard’s BGA Velectrik derailleur (see also French patent # 785,015).
This patent covers a simple (that word again) indexing mechanism delivered by making small indents in the slot along which the mechanism slides.
All the examples of BGA Velectrik derailleurs that I have seen do not have these indents - they have the plain vanilla slot shown in French patent # 785,015.
Browse associated derailleurs.
BGA Velectrik 1935?