DISRAELI DOCUMENTS
This leaflet celebrates 25 years of the Le Cyclo helically driven derailleur. It refers to it just as le Cyclo - not as the Cyclo Touriste. I think the Le Cyclo derailleur dates from 1924 - so I think this leaflet possibly dates from 1949.
Describing the early development of the derailleur, the blurb acknowledges the role of Paul de Vivie - but ignores everyone else.