This patent shows what looks like a Super Champion Mondial 45 but fitted with some kind of chain de-tensioner. I can’t quite work out exactly what the second cable is supposed to be doing - as it seems to be controlled by the same lever movement as the main gear shifting cable. Can you work it out?
You may also notice that Oscar Egg applied for this patent in Paris at 16:37 on the 7th June 1944. This was the day after D-Day. So you’re sitting at home and hear on the radio that the largest amphibious landing is history is happening in Normandy as a massive allied army tries to liberate France from the Germans - so you naturally think ‘it’s a perfect day for applying for a derailleur patent...’ - I know I would.