Aegler SA was a maker of watch movements based in Bienne/Biel. It was renamed Manufacture de Montres Rolex SA (colloquially Rolex Bienne or Rolex Biel) and was the primary supplier of movements for Rolex for decades until being purchased in 2004.
Jean Aegler opened a factory in Bienne in 1878, specializing in small watch movements. His son, Hermann Aegler began working with the firm, Wilsdorf & Davis, in 1905, supplying the London watch company with movements. After the firm began branding its watches "Rolex" in 1908, Hans Wilsdorf asked Aegler to dedicate all of its production to his firm. The company soon built a new factory building.
Wilsdorf & Davis moved to Geneva in 1919, having changed its name officially to Rolex four years earlier. Since it was exclusively supplying movements to them, Rolex took an ownership in the Aegler factory. Soon, Wilsdorf began seeing it as part of his firm's "family".
Although still owned primarily by the Aegler family, the factory complex in Bienne erected a famous sign, "ROLEX", along with the company's signature crown on the roof. The company was known as Manufacture de Montres Rolex, or simply "Rolex Bienne" or "Rolex Biel" for most of the century.
Aegler produced the famous Perpetual movement, invented by Aegler employee Emile Borer. Other famous products of the Aegler factory include the Datejust and Day-Date movements, and the Parachrom hairspring material.
In 2004, owner Harry Borer finally sold the firm to Rolex for a reported CHF 1-2 billion. The company soon began to expand the Bienne operation.