This card was issued in 1977 by Editions Rencontre as a part of their card based encyclopedia. It describes, in some detail, how to calculate the 'développement' of any given gear on a bicycle.

I warm to the idea that 3.571 is the 'fruit' of dividing 50 by 14. It's reassuring that the French (OK, the French-speaking-Swiss) can always find a way of relating anything back to food.

• Publisher: Editions Rencontre
• Country: Switzerland
• Date: 1977
• Derailleur brands: Simplex
• Derailleurs: Simplex SLJ5000 Gold