I would have expected the derailleur world of the 1920s to be busier than it was. The flowering of activity and invention in 1910 - 1914, killed by the First World War, was not properly repeated until the 1930s. However, there were two notable developments:

• The French cycle manufacturers slowly but surely recovered from the shock of the First World War. In particular, Le Chemineau built a strong business, dominating the derailleur market in the first half of the decade.
• In 1923, Albert Raimond released his seminal ‘Le Cyclo’ derailleur, starting a bitter personal feud, and fuelling intense commercial competition, with Joanny Panel’s ‘Le Chemineau’. By the end of the decade Cyclo was the new king.

As with the previous two decades, it is striking that every derailleur system shown is French.