Idéal is the brand of Les Établissements Claudius Jacquemard, based, almost inevitably, in St-Étienne, France. The company was founded in 1906 and specialised in the manufacture of hubs, freewheels and integrated cassette hubs with built in freewheels. In the tradition of Shimano and SunTour, this led Idéal to dabble in the manufacture of derailleurs.

I am aware of three Idéal derailleurs that made it into production. They are:

• A 1931 three speed model that involved the guide pulley sliding along two angled rails (see French patent # 723,162). The angle of these rails means that the derailleur maintains a fairly constant chain gap, and as such, mirrors some of the features of SunTour’s slant parallelogram design.
• A similar, but slightly different, two speed model that may also date from 1931, but was definitely in existence in 1935.
• A more refined three speed design from 1938 that featured a more substantial sliding rod that again was angled to follow the profile of the freewheel (see French patent # 848,964).

Claudius Jacquemard also held three other patents for derailleur designs:

• French patent # 738,147 from 1932 for a rather skimpy racing derailleur.
• French patent # 767,154 from 1934 for a basic fork-type derailleur.
• French patent # 807,506 from 1935 for a more sophisticated fork-type derailleur.

I do not know if any of these made it into production.

I also do not know what became of the company, but I have seen adverts that indicate that a company called Établissements Jacquemard of St-Étienne was selling venetian blinds under the Ideal brand during the 1950s.