Universal Geneve and Büren simultaneously launched movements with micro-rotor automatic winding in 1958. Both the Universal “Microtor” Cal. 1-69 and Büren “Super Slender” measured about 4.2 mm thick, but this nevertheless made them the thinnest automatic movements in the world. Piaget would definitively take the crown the following year with their 2.3 mm Cal. 12p, however. Universal's new Polerouter model was put to the test that year in a Greenland expedition by French and Swiss explorers.
In 1966, Universal introduced the Cal. 2-66, which measured just 2.5 mm thick. This narrowly bested the Büren Intramatic but could not beat Piaget. There is no evidence that Universal used the “Microtor” brand on this watch, though it is usually included under that name today.
Universal revived the “Microtor” movement in 2006, even recalling some retired watchmakers to help. The result was the Microtor UG100, a limited re-edition of the classic 2.5 mm Cal. 2-66 beating at 28,800 A/h. Cal. UG101 followed in 2007, updated for modern industrial production with 30 jewels and 44 hour power reserve.