The Tudor North Flag M91210N is the original 40 mm North Flag, powered by the manufacture calibre MT5621. Its defining feature is a power-reserve display—not the GMT function found on Tudor’s redesigned 2026 Northflag. The original offers a 70-hour stated reserve, date display and 100 m water resistance. It was documented on an integrated steel bracelet and on a black leather strap; published prices for those versions are historical, not current market valuations.
What the reference M91210N identifies
M91210N refers to the original Tudor North Flag. That distinction matters because Tudor’s 2026 Northflag is a substantially redesigned GMT model with a different movement and display. This review covers the original watch and treats the newer generation separately below.
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The North Flag also marked a milestone in Tudor’s company history. Tudor says the name refers to the British North Greenland Expedition and describes Tudor watches being issued to expedition members in the 1950s. In its 2015 press materials, Tudor stated: “In 2015, North Flag and Pelagos become the first TUDOR models to be fitted with movements developed and produced by the brand itself.”
Original Tudor North Flag M91210N specifications
| Specification | Original North Flag M91210N |
|---|---|
| Case diameter | 40 mm |
| Case height | Approximately 13.4 mm |
| Case and bezel | Brushed steel case; steel bezel with a matte black ceramic middle section |
| Crystal and case back | Flat, anti-reflective sapphire crystal; sapphire display back |
| Water resistance | 100 m |
| Dial and markers | Matte black dial with raised white numerals and indices filled with Super-LumiNova |
| Hands and displays | Luminous white hour and minute hands; yellow seconds hand with luminous tip; power-reserve indicator at 9 o’clock; date at 3 o’clock |
| Movement | Automatic, bidirectional Tudor calibre MT5621; COSC-certified; 4 Hz; silicon hairspring |
| Functions | Hours, minutes, seconds, date and power-reserve indication |
| Stated power reserve | 70 hours |
Specifications are from Monochrome Watches’ reference-specific review. Tudor Boutique Osaka’s 23 May 2021 listing independently identifies the bracelet reference as a 40 mm watch with MT5621, around 70 hours of reserve and 100 m water resistance.
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Design and the power-reserve display
A functional, high-contrast dial
The original’s black dial, white luminous markers and hands are set off by a yellow seconds hand. The date sits at 3 o’clock, while the power-reserve disc occupies 9 o’clock. That left-side indicator is the watch’s most distinctive functional detail: it makes the remaining reserve visible on the dial, rather than giving the North Flag a 24-hour hand.
Steel case, ceramic detail and display back
The 40 mm brushed steel case is paired with a steel bezel whose matte black ceramic middle section echoes the dial. The flat sapphire crystal has anti-reflective coating, and the sapphire case back exposes the movement. The documented case height is approximately 13.4 mm. These measurements give a useful basis for assessing fit, but do not establish how the watch will wear on a particular wrist.
Rank #2
- 41mm steel case with polished and satin finish
- Bidirectional rotatable bezel in steel with 24-hour graduated anodised aluminium disc
- Self-winding mechanical movement with 70 hour power reserve
Movement: calibre MT5621
The MT5621 is an automatic, bidirectional-winding calibre with COSC certification, a silicon hairspring and a frequency of 4 Hz. It drives the central time display and seconds, date and power-reserve indication. Tudor’s stated reserve for the original is 70 hours. Do not confuse that movement with MT5652-U, which powers the 2026-generation GMT Northflag.
Bracelet and leather versions
The reference family was documented in two configurations. Monochrome lists the bracelet model as M91210N-0001 and the leather version as M91210N-0002. Its descriptions identify an integrated three-link steel bracelet for the first, and a black leather strap with yellow stitching and lining for the second. Confirm the exact reference and supplied configuration when evaluating an individual watch; the model-family specifications alone do not establish what a particular pre-owned listing includes.
Rank #3
- Water resistance depth: 100.0 meters
- Case diameter: 38.0 millimeters
- Item shape: Round
- Department name: mens
- Calendar type: Date
Published prices and what they mean
| Configuration | Published price | Source and date basis |
|---|---|---|
| M91210N-0001, three-link integrated steel bracelet | €3,460 | Historical price reported by Monochrome Watches at publication; not a current asking price |
| M91210N-0002, black leather strap with yellow stitching and lining | €3,360 | Historical price reported by Monochrome Watches at publication; not a current asking price |
| Bracelet reference, Japanese listing | ¥415,800 | Tudor Boutique Osaka / OOMIYA, 23 May 2021; regional price at that date |
These are dated retail figures, not evidence of today’s resale value. A current M91210N market price is not established here; the price of an individual pre-owned watch depends on its specific condition and offering.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How the original differs from Tudor’s 2026 Northflag
Tudor’s official family page describes the 2026 Northflag as a return in a new design, with GMT functionality and Master Chronometer certification. Its specifications are not specifications for M91210N.
Rank #4
- .Hand-stitched with high-strength nylon thread, it is sturdy and less likely to crack
- Easy to install and replace without tools
- Special surface treatment, resistant to daily splashing water and sweat erosion.
- Skin-friendly leather inner layer, no indentation after long-term wearing
- Worry free after-sales service: We provide a "180 day worry free replacement" service. Is the strap fading? Does the texture not match? If there is no human damage, we will replace it directly! If you need customization, please contact customer service. Welcome to your purchase
| Feature | Original M91210N | 2026-generation Northflag |
|---|---|---|
| Movement | MT5621 | MT5652-U |
| Certification | COSC | COSC and METAS |
| Primary distinctive display | Power-reserve indicator | 24-hour GMT hand and graduated 24-hour rehaut |
| Stated reserve | 70 hours | 65 hours |
| Case | 40 mm steel; approximately 13.4 mm high | 40 mm 316L steel; height not stated on Tudor’s cited family page |
| Dial and markers | Matte black dial; raised white luminous numerals and indices | Black dial with monobloc ceramic luminous hour markers |
| Bracelet | Documented three-link integrated steel bracelet; leather version also documented | Two-link integrated bracelet with T-fit clasp |
| Water resistance | 100 m | Not stated on Tudor’s cited family page |
| U.S. list price | Not established as a current price | $5,525 on Tudor’s official U.S. listing accessed 5 October 2026; applies to the new generation, not M91210N |
Tudor says the redesigned 2026 watch retains the general lines and distinctive design elements of the 1973 Ranger II. Its GMT function, 65-hour reserve and U.S. list price belong to that current-generation listing and should not be attributed to the original reference.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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