Tudor Caliber MT5621

Manufacturer	Tudor
Caliber Number	MT5621, MT-5621
In-House?	Yes
Diameter	33.8mm
Height	6.5mm
Vibrations Per Hour	28,800 bph (4 Hz)
Power Reserve	70 hours
Jewel Count	28
Hacking Seconds?	Yes
Hand-Windable?	Yes
COSC?	Yes
Functions	Central hours; central minutes; central sweeping seconds; date at 3:00; power reserve indicator at 9:00
Country of Manufacture	Switzerland, Swiss made
Known Models	Tudor North Flag – Ref: M91210N-0001 (steel bracelet), M91210N-0002 (black leather strap)

The Tudor caliber MT5621 automatic caliber is an in-house Certified Chronometer (COSC) movement. It is equipped with a bidirectional rotor system and variable inertia balance, micro-adjustment by screw. This caliber also features a non-magnetic silicon balance spring – a first for Tudor (aka Rolex).

In Tudor’s own words:

“This movement provides impressive autonomy. Its power reserve of approximately 70 hours means that its wearer can, for example, take off the watch on Friday evening and put it on again on Monday morning without having to wind it. Beating to a frequency of 28,800 beats/hour or 4Hz, the movement is regulated by a variable inertia oscillator with silicon balance spring, held in place by a traversing bridge fixed at both sides to improve resistance to shocks and vibrations. Its self-winding system is bidirectional. The movement is certified by the Swiss Official Chronometer Testing Institute (COSC).” (Source: https://www.tudorwatch.com/en/inside-tudor/watchmaking/movement-5621)

Additional Resources:

• Tudor official site