The GMT is equipped with the calibre 100.8 in a high-artistic finish and the sapphire crystal back reveals the elaborate mechanics of the calibre. It features the characteristic components of the Moritz Grossmann movements, such as the 2/3 plate with the raised gold chatons, the Grossmann ratchet, the separately removable winding unit with pusher mechanism and the cantilevered balance cock with micrometer screw, as well as the mass-optimised balance.
On the GMT, the mechanism for the second time is integrated into the movement on the dial side. The 24-hour display is transmitted via the hour wheel of the centre time to another hour wheel and an intermediate wheel to the ring of the second time zone.
The second time zone display can be adjusted via the second crown at 10 o’clock. A ratchet wheel with ratchet spring is used to adjust the time in the pre-defined hourly gearshifts.