TUDOR Black Bay GMT M79830RB-0001: specifications and what to check

Aluminium, and what aluminium does

TUDOR specifies the bezel insert as a 24-hour graduated anodised aluminium disc in matt burgundy and blue.

Not ceramic. That single word changes how you grade it, how you describe it and what you promise.

Ceramic is close to unscratchable and fails by chipping — a bright flake at an edge, and nothing in between.

Anodised aluminium does the opposite. It fades, especially on coloured inserts and especially under sunlight, and it dents, taking small permanent marks where it has been struck. It does not chip in the ceramic sense.

So a used example with a paler burgundy than the catalogue photograph is displaying ordinary ageing, not damage. Some buyers actively prefer it. What you should look for instead is uneven fade — one sector noticeably lighter, which suggests the watch sat in a display case in one position for years — and dents around the edge.

Describe the material by name. A buyer cross-shopping against ceramic-bezel watches is entitled to know which they are getting.

Forty-eight notches, both directions

The bezel is specified as bidirectional rotatable with 48 notches.

Both halves are testable and both are worth testing.

Bidirectional is correct here. Diving bezels are restricted to a single direction so that an accidental nudge can only ever add to the time shown; a bezel that indexes time zones carries no such risk, so two-way movement is the specification rather than a defect.

Forty-eight notches means the bezel indexes in half-hour steps across twenty-four hours. Run it through a complete revolution and feel for detents that are soft, missing or gritty — and then set it against a marker, let go, and confirm it stays put. A bezel that creeps has made the second time zone unreadable.

Same movement as the Pro, different watch

The Manufacture Calibre MT5652 here is the same one TUDOR fits to the Black Bay Pro: COSC certified, bidirectional rotor, built-in architecture, approximately 70 hours.

What separates the two references is everything outside the movement:

• Case — 41mm here, 39mm on the Pro
• Bezel — bidirectional rotatable with an aluminium disc here; fixed satin-brushed steel on the Pro
• Clasp — a folding clasp with safety catch here; a T-fit rapid adjustment on the Pro

A listing that leads with "MT5652, 70 hours, COSC" has described both watches and identified neither.

Test the second zone over a day

Setting a GMT hand takes a moment. Proving it works takes twenty-four hours.

Put the 24-hour hand at a known distance from local time, leave the watch untouched, and come back the next day. The gap between the two readings should be unchanged. Drift there is a movement fault and no amount of counter-side inspection will show it.

With 70 hours of reserve you can run that test with the watch off the wrist.

Crown, tube and crystal

TUDOR calls out the crown and its tube: a steel screw-down winding crown with the TUDOR rose in relief, on a circular satin-brushed steel winding crown tube.

A separately specified tube is worth a look, because the tube is part of the case and a damaged one is a case repair rather than a crown swap. Thread the crown down several times; it should catch cleanly and sit flush.

The crystal is domed sapphire over a black, domed dial. Domed sapphire stands proud of the bezel, so tilt the watch and travel its edge under a raking light looking for chips.

200 metres, riveted steel bracelet, folding clasp with safety catch, and a stated five-year transferable guarantee requiring no registration or scheduled servicing.