Geneva Watch Days 2025: The COSC and the ultimate calibration challenge

At this year’s Geneva Watch Days, the Contrôle Officiel Suisse des Chronomètres (COSC) is participating for the first time with a precision competition.

The renowned non-profit organization for voluntary self-regulation of Swiss watch and watch movement manufacturers was founded in 1973 and tests the accuracy of watch movements manufactured in Switzerland, which are later installed in watches of Swiss origin.

COSC and the Competition of Precision

In the Calibership competition, amateurs and professionals demonstrate their regulating skills on Sellita watch movements. The calibers are tested by the COSC.

During the week, participants take turns presenting at the Culture Club, right next to the pavilion in the “Rotonde du Mont-Blanc”, the central meeting point of the Geneva Watch Days.

The amateur participants are supervised by students from the Geneva Watchmaking School. The goal is not only to impart skills but also to awaken a passion for watchmaking.

The official chronometer testing standards of the COSC are used as evaluation criteria.

The Calibership Challenge is supported by leading figures in the watch industry, including: