Why it matters
For most of its history, Tudor ("the brand for the working man") sat in Rolex's shadow with ETA-based movements inside its watches. From 2015 onwards, that changed: the new Tudor manufacture in Le Locle started producing in-house calibers branded "MT" (Manufacture Movements). The MT5612 was the first of the family; later siblings include the MT5602 (no date), MT5621 (with power-reserve indicator on the Pelagos LHD), MT5641/MT5602 series, and the chronograph MT5813 (Breitling B01-based). By 2026 every "Tudor" branded with an MT-prefix calibre is using in-house movement architecture; the older 2824-based Tudors are sliding into the pre-owned market.
Architectural choices
Three things mark the MT5612 as a serious manufacture caliber, not just a re-skinned Sellita. Free-sprung balance with variable-inertia weights: same approach Rolex Microstella, Patek Gyromax. Adjusts rate by moving weights on the rim, not by bending a regulator pin against the hairspring. More precise, more shock-resistant, more expensive to make. Silicon hairspring: completely non-magnetic, not affected by gravity orientation, lighter than steel. Tudor was ahead of Rolex on adopting silicon by ~9 years. 70-hour power reserve: one of the longest at this price point, achieved with a thicker mainspring barrel rather than a slower frequency.
How it compares to the Rolex 3235
The MT5612 and the Rolex 3235 are distinct movements; Tudor and Rolex share corporate ownership but not movement designs. The MT5612 was launched in 2015 (same year as the 3235) but was developed independently in the new Tudor manufacture. Comparison: MT5612 is 31.8 mm vs 3235's 28.5 mm (the MT is bigger, made for thicker tool-watch cases). MT5612 has a silicon hairspring; 3235 has Parachrom Bleu (the new Rolex 7140 also has silicon, but only from 2024). MT5612 is COSC certified; 3235 is Superlative Chronometer (-2/+2 in case, tighter than COSC). Both have 70-hour reserves and free-sprung balances. The 3235 is finished to a higher standard; the MT5612 is the sturdier, larger, more dive-watch-oriented architecture.
Watches it powers
Pelagos 25600 / 25610 (2015+), Black Bay 41 (M79540), Black Bay 36 (M79500) (uses the no-date MT5400), Black Bay 58 (M79030) (uses MT5402), Black Bay GMT (M79830RB) (uses MT5652, MT5612 with GMT module), Black Bay Chrono (M79350) (uses MT5813, Breitling B01-based). The Pelagos LHD (left-hand) uses the MT5621 with power-reserve indicator. By 2026 the MT family covers the entire Tudor catalogue except a few entry-tier Heritage and Royal references that still use ETA / Sellita.
Pelagos vs Black Bay calibers
The Pelagos and the Black Bay 41 use essentially the same MT5612 architecture, but in different tunings. Pelagos: regulated tighter (Tudor claims -2/+4 sec/day in their own internal "Master Chronometer-equivalent" tests, not externally certified beyond COSC). Black Bay 41: standard COSC -4/+6 regulation. Both are 70-hour, silicon hairspring, free-sprung balance. The Black Bay 36 and 58 use the smaller MT5402 / MT5602 variants (no date, slightly smaller diameter). For the Black Bay 58 GMT, see our Black Bay 58 page.
Service notes
Service for an MT-series Tudor caliber currently runs CHF 500-700 at Tudor and CHF 350-450 at qualified independents (the silicon hairspring and free-sprung balance need specialist tooling, but most modern watchmakers can handle it). Service interval is 10 years, longer than typical entry-tier Swiss workhorses, made possible by the silicon hairspring (no magnetism worries) and modern oils. Parts availability is good through Tudor service centres; aftermarket independents need authorised parts access. The MT5612's biggest service advantage over a 2824-2 Tudor: no magnetism vulnerability; you can wear it next to your laptop, on a magnetic clasp watch winder, or on a tool belt without rate concerns.
