TUDOR · Black Bay 54 and Black Bay 58
TUDOR M79000B-0001 vs TUDOR M7939A1A0NU-0001
10 published specifications differ between these two, and 5 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.
What differs
| Specification | TUDOR Black Bay 54, 37mm blue dialM79000B-0001 | TUDOR Black Bay 58, 39mm steel on braceletM7939A1A0NU-0001 |
|---|---|---|
| Case | 37mm stainless steel case with polished and satin finish | 39mm stainless steel case with polished and satin finishes |
| Diameter | 37 mm | 39 mm |
| Thickness | 11.2 mm | 11.7 mm |
| Bezel | 60-minute unidirectional bezel in stainless steel with aluminium insert devoid of minute graduations | Unidirectional rotatable bezel in stainless steel with anodised aluminium insert |
| Dial | Blue, domed, with applied hour markers | Matt black, domed, with applied hour markers |
| Crown | Stainless steel screw-down crown with the TUDOR rose in relief | Stainless steel screw-down winding crown with the TUDOR rose in relief |
| Bracelet | 3-link stainless steel bracelet with polished and satin finish | 5-link stainless steel bracelet with polished and satin finishes |
| Calibre | Manufacture Calibre MT5400 | Manufacture Calibre MT5400-U |
| Power reserve | Power reserve of approximately 70 hours | 65-hour power reserve |
| Certification | COSC | COSC and METAS certified |
What is identical
Worth knowing as much as the differences: these are the specifications you cannot use to tell the two apart.
- Lug width
- 20 mm
- Water resistance
- Waterproof to 200m (660 ft)
- Crystal
- Domed sapphire crystal
- Clasp
- TUDOR "T-fit" clasp
- Movement
- Self-winding mechanical movement with bidirectional rotor system
Stated for one, not the other
These rows cannot be compared, because one maker publishes the figure and the other does not. An empty cell is a gap in the manufacturer's documentation, not a gap in the watch — and not a licence to fill it in from the other column.
| Movement notes | Chronometer certified. Note this is the COSC calibre rather than the METAS-certified MT5400-U used elsewhere in the family. | not stated |
|---|
What the differences cost you
Each note below follows from the published figures in the tables above — what they mean for intake, for a listing, and for the handover. Nothing here estimates a price or a margin.
These reach different buyers
39 mm on the M7939A1A0NU-0001 against 37 mm on the M79000B-0001. Diameter is a poor predictor of how a watch actually sits, but it is the field buyers filter on, so the two land in front of different people. Do not let one listing's photographs or copy stand in for the other.
Different movements to verify and to service
The M79000B-0001 runs the Manufacture Calibre MT5400 and the M7939A1A0NU-0001 the Manufacture Calibre MT5400-U. Two consequences at intake: the service history that is normal for one calibre is not evidence about the other, and the calibre is the check that catches a movement swapped into the wrong case. Confirm the movement matches the reference rather than assuming it from the dial.
What to check on each
M79000B-0001
- Read the bezel insert carefully: TUDOR states it is devoid of minute graduations. An insert showing minute markings is not the one this reference ships with, and that is a substitution worth understanding before you buy.
- Check which MT5400 is fitted. This reference is specified with the COSC calibre, not the Master Chronometer variant, and conflating the two overstates what you are selling.
- Assess the case for over-polishing. At 37mm the lugs are slim to begin with, and an aggressive refinish shows on this size far sooner than on a larger watch.
M7939A1A0NU-0001
- Verify the calibre is MT5400-U rather than an earlier MT5402. The Master Chronometer version is a different movement, and the two are easy to conflate in a listing written from memory.
- Inspect the anodised aluminium bezel insert closely. Aluminium marks in a way ceramic does not, and insert condition is one of the larger swings in desirability on this reference.
- Work the five-link bracelet's T-fit clasp through its adjustment range, and check the links for stretch at the pins.
Sources
- TUDOR official product page for reference M79000B-0001 (Black Bay 54; 37mm steel case; steel bracelet) - Case: 37mm stainless steel case with polished and satin finish; Lugs: 20mm lug width; Case thickness: 11.2mm; Waterproofness: waterproof to 200m (660 ft); Bezel: 60-minute unidirectional bezel in stainless steel with aluminium insert devoid of minute graduations; Dial: blue; domed; with applied hour markers; Crystal: domed sapphire crystal; Movement: Manufacture Calibre MT5400 (COSC); self-winding mechanical movement with bidirectional rotor system; Power Reserve: power reserve of approximately 70 hours; Winding Crown: stainless steel screw-down crown with the TUDOR rose in relief; Bracelet: 3-link stainless steel bracelet with polished and satin finish with TUDOR T-fit clasp — retrieved 2026-09-22
- TUDOR official product page for reference M7939A1A0NU-0001 (Black Bay 58; 39mm steel case; steel bracelet) - Case: 39mm stainless steel case with polished and satin finishes; Lugs: 20mm lug width; Case thickness: 11.7mm; Waterproofness: waterproof to 200m (660 ft); Bezel: unidirectional rotatable bezel in stainless steel with anodised aluminium insert; Dial: matt black; domed; with applied hour markers; Crystal: domed sapphire crystal; Movement: Manufacture Calibre MT5400-U (COSC and METAS certified); self-winding mechanical movement with bidirectional rotor system; Power Reserve: 65-hour power reserve; Winding Crown: stainless steel screw-down winding crown with the TUDOR rose in relief; Bracelet: 5-link stainless steel bracelet with polished and satin finishes with TUDOR T-fit clasp; the unidirectional rotatable bezel rotates in one direction only and is deliberately harder to turn when the zero marker is at 12 o'clock to avoid inadvertent rotation — retrieved 2026-09-22
Not affiliated with TUDOR. Specifications are read from each manufacturer's own published documentation on the dates shown and may change; the manufacturer's current documentation governs.