This is a tantalising patent. It describes a rather thoroughly thought-out derailling fork mechanism to be used in combination with a chain tensioning arm - which is not described.

The inventor is Giovanni Galli of Torino - the founder of the Balilla and Galli brands, and the year is 1933 - which is very early for this kind of thing! It certainly looks at least as sophisticated as anything that Campagnolo or Vittoria had to offer at the time. Ah - what might have been!

• Publisher: Office de la Propriété intellectuelle (Belgium)
• Inventor: Giovanni Galli
• Country: Belgium
• Date: Priority date October 1933
• Derailleur brands: Balilla, Galli
• Derailleurs: unknown