French Patent # 995,861 - Huret

French Patent 995,861 - Huret main image

This, September 1949, patent is not primarily concerned with a derailleur - it really covers a, moderately bonkers, double gear lever that controls both front and rear derailleurs from a single mount on one side of the frame.

However it does show an interesting drawing of a derailleur which is somewhat similar to the Huret Compétition - but with its top pulley concentric with the pivot of the pulley cage. This is in contrast to the production Huret Compétition. One of the most advanced features of the production Huret Compétition (the design of which was patented a month after this patent here) was its offset pulley cage.

The drawing in this patent possibly indicates that early prototypes of the Huret Compétition had a concentric top pulley - which would not be that surprising given that Huret's touring twin-pulley design, the Huret Route Touriste, had a concentric top pulley. The main competitor of the Huret Compétition, the Simplex Tour de France, also had a concentric top pulley.

Or, of course, the whole thing might just be a case of 'artistic license'.