Black Bay GMT

Replicas targeting the Black Bay GMT, often using ETA or Sellita GMT base movements that lack the bidirectional independent GMT function.

• Snowflake hand proportions off: too narrow, too tapered, or with wrong lume plot shape -- this is the easiest single check
• GMT hand that moves with the local hour hand rather than advancing independently at crown position 1
• Bicolor bezel with a color join that is not sharp at the 6/18 division
• Tudor caseback markings with incorrect text layout or the wrong Tudor shield proportion

Genuine Black Bay GMT cases fitted with non-MT5652 movements from other Tudor references or third-party GMT calibers.

• Power reserve shorter than 60 hours from full wind
• GMT hand that cannot be independently set
• Movement sounds or beat rate inconsistent with 28,800bph

Original: Tudor's snowflake hands are wide and flat with a square lume plot inset near the tip. The profile is distinctive: the hour hand is broader relative to its length than most sport watch hands. Reproductions frequently get the proportions wrong -- either too narrow, too pointed, or with incorrectly shaped lume plots.

• Hour hand with a tapered or pointed profile rather than the flat wide rectangle of the genuine snowflake
• Lume plots that are round rather than rectangular, or that do not extend to the correct proportion of the hand width
• Seconds hand that does not match the lighter, thinner snowflake profile -- the seconds hand is also wider-than-normal but distinct from the hour and minute hands
• Hands with polished surfaces rather than the correct matte finishing of the genuine snowflake hands

Original: Tudor MT5652 is an in-house automatic GMT, 28,800bph, 70-hour power reserve, 26 jewels. METAS-certified. The GMT hand advances independently via the crown at position 1 in one-hour increments without stopping the seconds hand.

• GMT hand that cannot be set independently at crown position 1 -- if the GMT hand only moves with the local hour, the movement does not have a proper GMT function
• Power reserve depleting in under 48 hours from full wind -- the MT5652 is rated 70 hours; under 50 hours suggests a different movement or a worn mainspring
• Caseback showing a movement without Tudor hallmarks: the MT5652 caseback has Tudor branding and the MT designation visible through the caseback if exhibition; solid caseback has Tudor markings on the outside
• Seconds hand that stops during local hour adjustment -- on the MT5652, the local hour hand adjusts without stopping the seconds hand

Original: Aluminum bicolor bezel with a 24-hour scale. Aluminum is softer than ceramic; genuine Tudor aluminum bezels will show normal wear marks from use, but should not have scratches inconsistent with the watch's overall condition. The color join is clean and sharp at the 6/18 position.

• Color join between the two halves that is not sharp or is offset from the 6/18 position on the 24-hour scale
• Bezel insert with a sheen or color inconsistent with Tudor's aluminum specification
• Single-color bezel on a stated Black Bay GMT -- the bicolor bezel is standard for this reference

• Solid caseback with Tudor shield and rose hallmark at center
• "TUDOR BLACK BAY GMT" on the outer ring
• "MANUFACTURE MOVEMENT" designation on later examples
• "200M / 660FT" water resistance rating
• Reference M79830RB and serial number on the case midband between the lugs
• METAS certification mark on movement-facing side (visible if caseback removed)