Gruen, Rolex and Aegler
One of the most deeply-held myths about Gruen is that Gruen and Rolex at one time manufactured movements for each other's watches. This is not true, although both firms did use some of the same movements—the best known examples are the Gruen Techi-Quadron and its twin, the Rolex Prince. In reality, these movements were manufactured by a third company, Aegler, who was a very close neighbor to the Gruen Precision Factory.