This paragraph seems to claim that Nivex manufactured two different versions of their derailleur:

• A version for 'course' and 'grand sport' which has a capacity of 16 teeth.
• A version for 'cyclotourisme' which had unlimited capacity.

The difference lies in the length of the pulley cage. Each version is available in either clamp-on or braze-on forms.

(Source gallica.bnf.fr/ Bibliothèque nationale de France)

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• Publisher: L'Officiel A.C.M.
• Country: France
• Date: June 1951
• Derailleur brands: Nivex
• Derailleurs: Nivex course, Nivex cyclotourisme (1st style)