Mercier is a French brand of bicycles and cycle components. The company was founded by Emile Mercier in 1919, originally to manufacture bicycle parts, but started producing complete bicycles in about 1930.

Mercier was famous for its racing bikes, and had a long history of sponsoring teams in the Tour de France. Amongst of its more notable riders were Antonin Magne, Louison Bobet, Raymond Poulidor, Joop Zoetemelk and Cyrille Guimard

Emile Mercier died in 1973 and his company died not long after, filing for bankruptcy in 1985. The Mercier brand name is currently owned by the Accell Group - one of Europes largest bike manufacturers.

In terms of derailleurs, I have heard tell of four designs:

• Mercier adopted a 'touring' design that was patented by Novitas Fabrik elektrischer Apparate A.G. of Zürich, Switzerland in 1932 and named it the Mercier Valor.
• Frank Berto reports that, in 1933, Mercier designed a rod operated racing derailleur for Francis Pélissier. He claims that Stronglight bought the design in 1935.
• In 1934 Mercier patented their own design of 'racing' derailleur, called the 'Super Valor' with a layout somewhat similar to the 1936 Charvin GRI-GRI Course. This derailleur was definitely advertised for sale in 1935.
• In 1935 Mercier also advertised another derailleur under the 'Super Valor' name. This was a fork type system with a separate chain tensioning arm - very similar to the best-selling Super Champion design.