Editorial
The Black Bay GMT (ref. M79830RB-0001) is Tudor's traveler's-GMT, 41mm steel, red/blue 'Pepsi' bezel insert in aluminium, and the in-house MT5652 caliber with an independently-jumping local hour hand. Launched in 2018, it answered the long-standing 'why can't I have a GMT-Master at half the price?' question without compromising on the one specification that matters: the local-hour-jump that makes a GMT useful in actual travel.
Tudor announced the Black Bay GMT at Baselworld 2018, a year that also saw the Pelagos LHD GMT and a renewed focus on Tudor's in-house movement portfolio. The MT5652 caliber is a chronometer-certified GMT with a 70-hour reserve and a true traveler-GMT layout (jumping local hour hand, not the cheaper office-GMT layout where only the 24-hour hand is independent). Bezel-insert variants ship in red/blue ('Pepsi') and a later black/grey ('Earl Grey') and the 'Opaline' silver dial.
The Coke-style red/black bezel is not a factory Black Bay GMT issue.
Common things to check: bezel insert (aluminium, not ceramic, fading and minor scratching are normal on used examples; severe denting is a service item); crown function (the GMT crown layout has three positions, verify the local hour hand jumps independently in position 2 and the date moves in position 1); bracelet (the riveted-style bracelet is the canonical option; rubber, fabric, and aged-leather straps also ship factory, verify the bracelet against the box contents); the MT5652 caliber is robust, but the GMT module adds wear surfaces that benefit from a service every 7-10 years; a heavily-traveled example with no service history should be priced with a service factored in.
