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Mass-produced#4 in family

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In-house manufacture caliber · caliber Ulysse Nardin Caliber UN-150 (automatic, flyback chronograph, silicon components, 60-hour power reserve) · 60h power reserve (2.5 days)
Large case: suits wrists 7 in+ (18 cm+)
44 mm case. A bold, statement-size wear. Best suited to larger wrists where the case sits flush.

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Authentication

In-house flyback chrono in a dive case; flyback reset must be instantaneous and unidirectional bezel ratchets counterclockwise only.

Known issues in the market
  • Flyback reset delay indicates mechanism wear.
  • Screwed-down pushers and crown must thread smoothly; cross-threading indicates improper reassembly.
AreaWhat to checkWhat is correctRed flag
caseUnidirectional bezel ratchet directionBezel ratchets counterclockwise only; clockwise movement is locked per dive watch safety standardBezel rotates in both directions; diver safety feature compromised
crownCrown and pusher thread conditionCrown and both pushers thread down smoothly with no resistance or cross-threadingCross-threading; pusher will not lock down; gasket or thread damage
movementFlyback reset speedInstantaneous chronograph reset on flyback pusher activationDelayed reset; mechanism wear
Common legitimate replacements
  • Rubber dive strap; UN OEM preferred.
  • Crystal; sapphire with AR coating standard.
Expert resources: Ulysse Nardin Diver Chronograph press materials. UN-150 silicon escapement documentation.

Authentication guide

Last reviewed June 2026

The Diver Chronograph 44mm is UN's sport instrument: 200m water resistance, ceramic bezel, titanium case, and a flyback chronograph movement. The pushers are integrated into the crown-side of the case and sealed for water resistance. A non-functional pusher system is the most significant authentication red flag.

Known reproduction risks

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MEDIUM

Replicas of dive chronographs exist across many brands; UN-specific replicas are less common but the ceramic bezel and flyback function are the definitive tells.

  • Bezel surface that accepts key scratches (confirms non-ceramic)
  • Non-functional flyback reset: pushers that require stop-then-reset-separately rather than single-press flyback
  • Anchor logo absent from crown end face
  • Case finishing inconsistent with titanium: titanium is lighter than steel and has a characteristic matte-grey tone

Weighing the watch in hand is a useful informal check: titanium is approximately 40% lighter than steel. A Diver Chronograph that feels heavy like steel is not in a titanium case.

Dial variants by era

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EraDescriptionIdentifiers
2018 to presentCurrent production Diver Chronograph in titanium, 44mm. Blue or black dials with mixed numeral/index display. Ceramic unidirectional dive bezel.
  • Ceramic dive bezel with unidirectional rotation and correct 60-minute scale markings
  • Chronograph pushers integrated into the case at 2 and 4 o'clock positions
  • Screw-down crown for water resistance maintenance
  • Mixed numeral and index dial layout with large luminous hour markers
  • "Diver Chronograph" text on the dial
  • "Ulysse Nardin" text at 12 o'clock position
  • Anchor logo on the dial

Service part flags

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Chronograph pushers

Original: Two chronograph pushers integrated into the case, sealed for water resistance. The pushers should activate the chronograph start/stop and flyback reset functions with a firm, positive click. The flyback function resets and restarts the chronograph in a single pusher operation.

Replacement tells
  • Pushers that activate no chronograph function -- non-functional is a significant service issue
  • Pushers that start/stop the chronograph but do not perform flyback reset in a single press (indicates flyback mechanism failure)
  • Pushers with incorrect profile or finish level inconsistent with the titanium case
Ceramic bezel

Original: Unidirectional ceramic dive bezel. The ceramic is scratch-resistant: a key or knife will not mark the ceramic surface. Numerals are filled into the ceramic surface and sit at surface level.

Replacement tells
  • Bezel surface that accepts key scratches (ceramic does not; aluminum does)
  • Numerals that sit proud of the bezel surface rather than inset at surface level
  • Bezel that rotates in both directions -- genuine dive bezel is unidirectional for safety
  • Bezel with click positions that slip rather than engaging firmly
Screw-down crown and water resistance

Original: Screw-down crown for 200m water resistance. The crown should screw down firmly and the anchor logo should be visible on the crown end face.

Replacement tells
  • Crown without anchor logo engraving
  • Crown that does not screw down or has damaged threads
  • Crown with a profile inconsistent with the UN Diver specification

Case back markings

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2018 to present
  • Solid caseback for water resistance on the Diver Chronograph
  • "Diver" and "200m" water resistance marking on the caseback
  • "Ulysse Nardin" and reference marking on the caseback exterior
  • Reference 1503-155-3/22 and serial number on the case band
  • Titanium hallmark appropriate to the case material

Movement tells

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  • Cal. UN-150 in the Diver Chronograph is the flyback variant. The flyback reset function requires a single pusher press to stop, reset, and restart the chronograph simultaneously. Testing this function confirms the flyback mechanism is operational.
  • Silicon components in the escapement are visible through the caseback on exhibition-caseback variants. The Diver Chronograph uses a solid caseback, so movement verification requires opening.
  • Power reserve is approximately 60 hours. A fully wound Diver Chronograph stopping in under 50 hours warrants service.
  • Chronograph accuracy at 1/10-second resolution should be verifiable with a reference timepiece. Significant chronograph error on a recently serviced example indicates issues with the column-wheel regulation.
Sources: Ulysse Nardin -- Diver Chronograph specification and water resistance documentation; WatchUSeek -- UN Diver forum and authentication notes.

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