I can’t definitively explain why, but I think this derailleur is the Simplex Rigidex 30. I think French Registered Design # 46818-001 shows the Simplex Rigidex 35.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien Juy
• Country: France
• Date: French application October 1951
• Derailleur brands: Simplex
• Derailleurs: Simplex Rigidex 30?