In 1838, Winnerl then developed the first split-seconds mechanism. It had two superposed seconds hands that could be separately stopped and resynchronised. One of them indicated the beginning, the other one the end of an event. The time difference allowed the stopped time to be calculated.
Source: hautehorlogerie.org, lange-soehne.com
Application: Władysław Meller
Other records: Timeline of Watchmaking Innovations