This patent appears to be for the cunning device that limits the rotation at the rear knuckle of the Favorit PWB. While that may not be earth-shatteringly interesting, this patent does put a date on the Favorit PWB (which is shown as fully complete in every detail) and also names its designer; Václav Silovský.

• Publisher: Úřad průmyslového vlastnictví
• Inventor: Václav Silovský
• Country: Czech Republic
• Date: Czech application July 1964
• Derailleur brands: Favorit
• Derailleurs: Favorit PWB