TUDOR · Black Bay 58 GMT
TUDOR Black Bay 58 GMT M7939G1A0NRU-0003: specifications and what to check
A 39mm GMT rated to 200 metres, with a bidirectional 24-hour bezel rather than the unidirectional dive bezel the rest of the family uses. That single difference changes what the watch is for.
Reference M7939G1A0NRU-0003 · specifications read from the manufacturer on 2026-09-22 · listed as current
Specifications
As published by TUDOR. A field the manufacturer does not state is left out rather than filled in.
- Case
- 39mm stainless steel case with polished and satin finishes
- Diameter
- 39 mm
- Thickness
- 12.8 mm
- Lug width
- 20 mm
- Water resistance
- Waterproof to 200m (660 ft)
- Crystal
- Domed sapphire crystal
- Bezel
- 24-hour bidirectional rotatable bezel in stainless steel with black and burgundy anodised aluminium insert
- Dial
- Black, domed, with gilt applied hour markers
- Crown
- Stainless steel screw-down winding crown with the TUDOR rose in relief
- Bracelet
- 5-link stainless steel bracelet with polished and satin finishes
- Clasp
- TUDOR "T-fit" clasp
Movement
- Calibre
- Manufacture Calibre MT5450-U
- Type
- Self-winding mechanical movement with bidirectional rotor system, integrated GMT function
- Power reserve
- 65-hour power reserve
- Certification
- COSC and METAS certified
What to check before you buy
- Turn the bezel both ways. This reference uses a bidirectional 24-hour bezel, and a bezel that refuses to turn anticlockwise belongs to a dive reference, not this one.
- Check the colour split on the insert lines up exactly with the 24-hour graduation. A misaligned two-tone insert is immediately obvious and indicates the part has been off.
- Run the GMT hand through a full rotation and confirm it reads correctly against the bezel at both the day and night ends of the scale.
- Compare the gilt markers and hands for consistent tone. Gilt printing and applied markers should match each other; a replaced hand set often does not.
- Note the case is 12.8mm — a millimetre deeper than the time-only 58. Anyone cross-shopping the two will feel the difference, so do not quote one's dimensions for the other.
Bidirectional, and that is the point
Every other Black Bay on this site carries a unidirectional bezel that turns one way only, because a dive bezel must never be able to under-report elapsed time.
This one is bidirectional, graduated over 24 hours rather than 60 minutes, because it is doing a completely different job: tracking a second time zone against the GMT hand. Turning it the wrong way cannot hurt anybody.
That is the first thing to check on a used example, and it is genuinely diagnostic. A bezel on this reference that resists anticlockwise rotation has been fitted with the wrong part.
The insert has to line up
The insert is black and burgundy anodised aluminium, split between day and night halves of the 24-hour scale. That split is a reference point in a way a single-colour insert never is: if the colour change does not sit exactly on the graduation, the part has been removed and refitted badly, or replaced with something that is not quite right.
Aluminium also behaves as aluminium does — it marks, and it fades. Judge it as you would the insert on the time-only 58, where the same material rules apply.
A millimetre matters here
12.8mm deep against the time-only 58's 11.7mm. On paper that is nothing. On the wrist, on a 39mm watch bought specifically because it is the compact one, it is the difference people notice and comment on.
Do not quote the thinner reference's dimensions when selling this one. A buyer cross-shopping the family will have both numbers, and being caught rounding in your own favour costs more than the millimetre ever could.
Still a 200-metre watch
Worth saying plainly, because a travel complication often implies a dressier watch: this keeps the 200 metre rating and the screw-down crown of the dive references. It is a GMT built on a dive watch rather than a dress GMT, which is most of its appeal.
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Sources
Not affiliated with TUDOR. Specifications are read from the manufacturer's own published documentation on the date shown and may change; the manufacturer's current documentation governs.