This article reports on the 1951 Frankfurt bicycle show - along with a potted history of bicycle technology. Unsurprisingly this is from a German perspective - which is quite refreshing and interesting. The article was published on the VDI Nachrichten web site as part of its 100 year anniversary celebrations.
The interest for derailleur connoisseurs lies in the two images in the bottom right hand corner of the first page. One is of a Durex version of a Simplex Tour de France. The other is of the Kreis automatic 2-speed derailleur.