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.
Johann Aegler opened a factory in Bienne in 1878, with his son Jean Aegler taking over by 1886. The firm specialized in small watch movements, including pendant watches for ladies, remontoirs, and case finishing. The firm received one of the first Swiss patents, number 243, by 1890. Jean's widow had taken over the firm by 1894 and relocated it to Rue du Vignoble, now known as La Haute-Route, in the Rebberg/Vignoble hills above Bienne. The company would soon advertise as being located at the “Rebberg” factory, and this would soon become a brand of watches as well.
In 1906, the firm became known as Les Fils de Jean Aegler, as Jean's son Hermann Aegler took over. Hermann 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 increase production for his firm. The company officially renamed itself Les fils de Jean Aegler, Fabrique de montres Rebberg, Final & Rolex in 1912. Aegler SA continued producing watches under the Rebberg and Final brands, for a few years, focusing on ladies models. But the company was reorganized on July 30, 1914, becoming Aegler SA, Rolex Watch Co.
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 stake in the Aegler factory. Soon, Wilsdorf began seeing it as part of his firm's “family”. But Rolex Watch Co. of Bienne operated independently, with the Aegler family acquiring shares in Rolex and receiving a seat on the board after World War I.
Aegler had long supplied the American Gruen brand, and in 1925 officially registered as Aegler SA, Fabrique de Montres Rolex et Gruen Guild A. The products of the Aegler factory were sold in the United States as “Gruen” and in Europe, Asia, and the English Colonies as “Rolex”. Gruen suffered during the Great Depression, and focused exclusively on their own Precision Factory in Bienne. Aegler officially dis-associated itself from Gruen in 1936, with the company renamed Manufacture des Montres Rolex, Aegler SA at that time.
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.