Onofre Forton of St-Étienne is named as the applicant for French patent # 848,964, which is clearly for a design known to be used by Idéal. On this, rather thin, basis, I have assumed that this patent is also for an Idéal design - although I have no other evidence for this.
This design is for a strikingly simple, pull-chain, two speed fork-type derailleur. As such, it resembles many mid century front derailleur designs. Unusually, it also incorporates a plate to protect the derailleur form the top run of the chain.
I have no idea if it was ever manufactured.