A third-party quality assurance certification by the Swiss Federal Institute of Metrology (METAS). Watches submitted for METAS certification must first be COSC-certified. They are then tested for key functional characteristics including precision, resistance to magnetic fields, waterproofness and power reserve. METAS-certified watches are known as Master Chronometers and they boast outstanding performance ratings including 0/+5 seconds daily accuracy, 200m waterproofness, at least 70-hour power reserve, and magnetic resistance to 15,000 gauss. An example of a Master Chronometer with METAS certification is Tudor’s new Black Bay Ceramic, launched in 2021.