What it is
The MT5402 is the smaller-diameter sister of the MT5612 in the Manufacture Tudor (MT) caliber family. Both are designed and built at the Kenissi facility in Le Locle, the joint venture between Tudor and Chanel that supplies movements to Tudor, Chanel J12, Norqain, Bell & Ross, Breitling (in part), and others. The MT5402 was launched in 2017 with the redesigned Black Bay 41, and now powers the smaller Black Bay diameters (36 / 39 / 41 mm) and the Pelagos 39. Where the MT5612 is 28 mm in diameter (sized for 41 mm cases), the MT5402 is 26 mm (sized for 36-39 mm cases) but shares architecture, regulation tier, and finishing.
Key features
Free-sprung balance with variable inertia weights: Tudor's standard, regulated by the weights on the rim rather than a regulator pin. More shock-resistant, more consistent rate. Silicon hairspring: non-magnetic, temperature-stable, modern Swiss benchmark material. 70-hour power reserve: matches the modern industrial Swiss standard (Rolex 3235, Patek 324, Breitling B01). COSC chronometer: -4/+6 sec/day, Tudor's house standard since 2015. The MT5402 returns from regulation typically within ±2 sec/day, well inside the COSC envelope. Bidirectional rotor on ball bearings: efficient self-winding with low wear.
Where it appears
Black Bay 41 (since 2017): the modern 41 mm Black Bay reference. Black Bay 39: the 39 mm Black Bay (the most popular modern Black Bay diameter for many wrist sizes). Black Bay 36: the 36 mm dressy Black Bay variant. Pelagos 39 (2022): Tudor's no-date 39 mm titanium dive watch (smaller sibling of the Pelagos 42). Black Bay GMT (some references use the MT5652 with GMT module, others use MT5402-derivatives). The MT5402 represents the compact-Tudor strategy: a real 70-hour-reserve in-house caliber in a watch case sized for normal wrists, where competitors at this size typically use third-party calibers.
How it compares to the MT5612
The MT5612 (28 mm) is sized for 41-43 mm cases (Pelagos 42, Black Bay 41 GMT, North Flag); the MT5402 (26 mm) is sized for 36-41 mm cases (Black Bay 36/39/41, Pelagos 39). Both share the same architecture: 4 Hz, 70 h reserve, free-sprung balance, silicon hairspring, COSC, ball-bearing rotor. The smaller MT5402 has a slightly different gear-train layout to fit the smaller diameter but functionally identical. The MT5402 is also the base for the MT5602 (no-date variant for the Black Bay Fifty-Eight) and the MT5652 (GMT variant).
Service notes
Service for an MT5402-equipped Tudor runs USD 600-900 at Tudor service centres (typically through Rolex Service Centres, since Tudor uses the parent network), with a 2-year warranty. Recommended interval: 10 years, the modern industrial Swiss benchmark. Independent service is increasingly available for the MT family, as Tudor has not aggressively restricted parts (in contrast to Rolex). The free-sprung balance and silicon hairspring reduce wear and rate drift over the service interval. The MT5402 is among the most service-tolerant in-house Swiss calibers in the modern market.
