The TUDOR Prince Chronograph One was a one-off creation for Only Watch 2023, not a regular-production watch. Its 18k yellow-gold case and bracelet reinterpret the 1970s Big Block chronograph, while its prototype MT59XX calibre marked a new chapter in TUDOR’s exploration of column-wheel chronograph movements.
What is the TUDOR Prince Chronograph One?
TUDOR introduced the Prince Chronograph One as a unique piece for Only Watch 2023, the charitable watch auction. The brand listed it under reference 9420/801 and described its movement as a prototype—“number 0” in development. TUDOR also says the “XX” designation in its calibre naming is reserved for prototypes.
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That distinction matters: the watch is a singular concept and prototype showcase, not evidence that MT59XX became a regular production calibre or that this gold configuration entered TUDOR’s standard collection. TUDOR’s announcement identifies the piece as unique but does not establish its present ownership, sale status, or current value.
How does it draw on the Big Block?
TUDOR’s chronograph history dates the Big Block family to 1976, when the brand introduced its first self-winding chronographs. Their automatic rotor required a thicker case, inspiring collectors’ nickname “Big Block.” The original generation used the Valjoux Calibre 7750.
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The Prince Chronograph One takes that heritage as a starting point rather than reproducing one vintage reference. TUDOR’s historical account describes a varied family: reference 9430/0, for example, had a black dial with three white counters; “Exotic” versions used a roulette-like minute track and orange seconds hand; and some watches had square crown guards. The 79100 series arrived in 1989 with minimal modifications and continued the Big Block lineage. These details characterize particular versions, not every Big Block.
What movement is inside the Prince Chronograph One?
The watch uses TUDOR’s prototype MT59XX, a manufacture chronograph movement with a column wheel. TUDOR describes it as the beginning of its modern exploration of column-wheel chronograph movement manufacturing. It is distinct from the Valjoux 7750 used in the original Big Block generation; the two movements belong to different points in the watch’s story.
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- 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
- Regulating system: a variable-inertia oscillator with a silicon balance spring.
- Automatic winding: a tungsten monobloc rotor.
- Movement specifications: 30.8 mm diameter, 7.2 mm thickness, 40 jewels, and a frequency of 28,800 beats per hour.
- Power reserve: approximately 70 hours, as stated by TUDOR.
- Accuracy specification: TUDOR states a tolerance of −2/+4 seconds per day for the fully assembled watch.
These are manufacturer specifications published in 2023, not results of independent testing. TUDOR’s specification sheet also labels the watch a Swiss chronometer officially certified by COSC.
Prince Chronograph One specifications
| Specification | TUDOR’s 2023 listing |
|---|---|
| Reference | 9420/801 |
| Case | 42 mm, 18k yellow gold |
| Bezel | Fixed 18k yellow gold with black anodized aluminium insert |
| Dial | Black lacquer with sunken gold registers |
| Crystal | Sapphire |
| Water resistance | 200 m, stated by TUDOR |
| Caseback and bracelet | Solid gold caseback and matching three-piece bracelet |
| Calendar | Date at 3 o’clock |
| Chronograph and seconds displays | 30-minute counter at 12 o’clock; 12-hour counter at 6 o’clock; small seconds at 9 o’clock |
| Movement | Prototype calibre MT59XX; column-wheel chronograph |
| Power reserve | Approximately 70 hours, as stated by TUDOR |
| Movement frequency | 28,800 beats per hour |
| Movement dimensions | 30.8 mm diameter; 7.2 mm thickness |
| Jewels | 40 |
All figures in the table are from TUDOR’s 2023 press release and specification sheet for this unique Only Watch piece; they should not be read as specifications for a broader production line.
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What makes it different from a vintage Big Block?
The clearest differences are the movement, materials, and status. The original Big Block’s first generation used the Valjoux 7750, while the Prince Chronograph One houses a TUDOR-developed prototype. The new one-off is specified in 18k yellow gold, including its matching bracelet; TUDOR’s historical account presents Big Block references as a family with varied configurations rather than one uniform specification.
Design continuity is strongest in the chronograph concept and the deliberate nod to the thicker self-winding Big Block lineage. The gold case, black lacquer dial, sunken gold registers, and prototype calibre make the Prince Chronograph One its own interpretation—not a reissue of a particular vintage reference.
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