Tudor Black Bay GMT M79830RB-0001«Pepsi»

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The storyWhy this reference matters

Every Black Bay reissues something. The divers come from references 7922, 7016 and 94010; the Fifty-Eight from 1958. The GMT comes from nowhere: in Tudor's entire history there is no watch with a second time zone before this one, launched at Basel in 2018. It was assembled from parts borrowed in-house — snowflake hands from the divers of the late sixties, a riveted bracelet from the fifties — and a burgundy and blue bezel taken from the other side of the family.

The odd thing is that the invention works better than a lot of literal reissues. The bidirectional 48-click bezel doubles as a day-night indicator — blue covers six in the evening to six in the morning, burgundy the rest — and, because it turns, it lets you track a third time zone, which the Black Bay Pro with its fixed bezel cannot do. The insert is matte anodised aluminium, not the ceramic that was fashionable at the time.

Inside is the MT5652, Tudor's first in-house GMT calibre, and it's solved the expensive way: the hour hand jumps in one-hour steps and carries the date with it, rather than leaving the 24-hour hand to be set on its own, which is the cheap solution. That makes it a true traveller's GMT, the kind you adjust as you land. Add 28 jewels, 4 Hz, a silicon hairspring, 70 hours of reserve and COSC certification.

SpecificationsThe numbers, in one table

IdentificationHow to tell it apart

Forty-one millimetres, 14.6 thick, 50 lug to lug and 22 between the lugs. Bidirectional 48-click bezel with a matte anodised aluminium insert in burgundy and blue, domed black dial, snowflake hands, red GMT hand, date at three, crown without guards, domed sapphire and 200 metres of water resistance.

The 79830RB block always means the burgundy and blue bezel; what changes with the suffix is the dial and the strap. The -0001 is the black dial on the riveted steel bracelet and the -0003 is the same dial on a fabric strap. Since 2023 there are also opaline-dial references, such as the -0010. If somebody offers you a "79830RB" without telling you the suffix, they've told you nothing.

Against the 2024 Black Bay 58 GMT the distinction is colour and size: that one is 39 mm with a black and red bezel. Burgundy and blue at 41 mm is always this watch. And against the Black Bay Pro the rule is just as simple: the Pro has a fixed steel bezel and a yellow GMT hand; this one turns, and the hand is red.

CollectingWhat collectors check

Size first. Fifty millimetres lug to lug and 14.6 of thickness over 22 mm lugs make this the Black Bay with the most presence on the wrist, considerably more than the 41 of the diameter suggests. Anyone describing it to you as "an affordable Submariner" hasn't measured it: the Submariner is appreciably flatter and shorter lug to lug.

The bezel insert is anodised aluminium: it scratches, dents at the edges and loses saturation over the years, the burgundy half especially. It's a service part, so a brand-new insert over a marked case is a replacement, not a miracle of preservation. Check that the notch at twelve lines up with the dial and that the 48 clicks are crisp, with no back-play.

Two quick tests on the movement: that the hour hand advances in clean one-hour jumps, dragging the date with it, and that the GMT hand lands squarely on a marker of the 24-hour scale, because a poor fit is obvious at once. On the riveted bracelet, check the clasp for side play. And keep the paperwork: Tudor gives five years of transferable warranty with no registration required.

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