The COSC certificate is the most widespread label validating a watch's precision.  Respecting the ISO 3159 international norm, it ensures the accuracy of a movement, and rarely a finished watch. We visited one of the three workshops that control more than 1.6 million calibers every year to interview its director Andreas Wyss. He underscores one particular fact: even if the norm was implemented in 1976, the level of precision remains, in particular as the thousands of movements produced every day must respect it.