The PIONEER Mk I is the replica of the “Calibre 40”, the first precision chronograph produced by Hanhart in 1938. All of the chronograph functions on this unconventional model – start, stop and zero setting – are performed by a single button and always strictly follow each other. Unlike its two-button equivalent, the seconds hand on this chronograph cannot be restarted from the point at which it is stopped; the next press of the button invariably returns the spring to the original starting point. This meant that the automatic calibre used for the Mk I also had to be redesigned slightly.