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In-house manufacture caliber · caliber Rolex Cal. 2236: in-house automatic, 28,800bph, 55h PR, 31j; silicon Syloxi hairspring; used in Lady-Datejust 28; Rolex first silicon hairspring caliber · 55h power reserve (2.3 days)
Small case: suits slender wrists (under 6.5 in / 16.5 cm)
28 mm case. A compact, elegant wear. Particularly at home on narrower wrists where larger cases can overhang.

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Authentication

Cal. 2236 with the silicon Syloxi hairspring is unique to the 28mm Lady-Datejust; any larger-caliber rotor architecture is a movement swap.

Known issues in the market
  • Diamond-set dial and bezel variants require individual stone inspection; loose or missing stones reduce value significantly.
  • The Syloxi hairspring is proprietary to Cal. 2236 and cannot be confirmed by visual inspection alone; caliber number on movement is the check.
AreaWhat to checkWhat is correctRed flag
casebackCal. 2236 movement architectureCal. 2236 visible through caseback with rotor specific to this caliber; Syloxi hairspring not visible without magnificationCal. 3235 or other larger-caliber rotor architecture; any rotor that does not match Cal. 2236 specification
dialDiamond setting integrity on set dialsAll stones flush and secure with no visible movement under light pressure; prongs uniform and undeformedAny loose stone, missing prong, or stone with a different profile than surrounding stones
caseBezel diamond or metal conditionConsistent facet height across all bezel stones; metal bezel options have sharp edges with no roundingAny stone lower than its neighbors; flat or polished bezel edges on a set bezel variant
Common legitimate replacements
  • Diamond dials are sometimes replaced with non-diamond versions; verify dial matches what is documented in papers.
Expert resources: Rolex Lady-Datejust 279174 product documentation. Rolex Cal. 2236 technical specifications.

Authentication guide

Last reviewed June 2026

The 279174 is the current Lady-Datejust 28mm in Rolesor (steel and yellow gold) on an Oyster bracelet. Cal. 2236 -- a movement developed specifically for the ladies' line -- is the correct caliber. The smaller diameter makes quality differences very apparent at normal viewing distances.

Known reproduction risks

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HIGH RISK

Replica Lady-Datejust with incorrect proportions

  • Replica cases at 28mm frequently have disproportionately thick mid-cases relative to the genuine slim Datejust profile
  • Applied indexes on replicas are often too thick or too spaced for the smaller dial surface
  • The Rolesor bracelet finish alternates brushed steel center links and polished gold outer links; replicas often get the finish direction reversed or apply uniform finish throughout

Dial variants by era

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EraDescriptionIdentifiers
2017 to presentAvailable in silver, white, chocolate, and gem-set dials scaled for the 28mm case. Applied index proportions differ from the full-size Datejust.
  • Smaller applied baton indexes proportional to the 28mm case; visually narrower than 36 or 41mm Datejust indexes
  • Date window at 3 o'clock with Cyclops lens
  • Rolesor fluted yellow gold bezel on 279174 specifically
  • Oyster bracelet with Oysterclasp; center links in steel, outer in yellow gold

Service part flags

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Movement

Original: Cal. 2236 is a ladies' caliber with a Siroui silicon balance spring. It was introduced specifically for the current Lady-Datejust generation.

Replacement tells
  • Service documentation listing Cal. 2235 (predecessor), Cal. 2130, or any gents' caliber in a stated 279174
  • A conventional (non-silicon) balance spring; the Siroui spring is a flat-wave silicon spring visibly different from conventional metal hairsprings
  • Incorrect beat rate; Cal. 2236 runs at 28,800 bph
Bezel

Original: Fluted yellow gold bezel specific to the 279174; the fluting pattern is proportionally finer than the gents' Datejust fluted bezel.

Replacement tells
  • Bezel with fluting that appears too coarse for the 28mm case scale
  • Steel or plated bezel in place of solid yellow gold
  • Smooth bezel from a different Lady-Datejust reference (gem-set or smooth bezels are on different reference numbers)

Case back markings

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2017 to present
  • Solid steel caseback -- no exhibition window
  • Engraved: ROLEX OYSTER PERPETUAL LADY-DATEJUST
  • Rolex crown at center
  • Reference 279174 and serial between the lugs

Movement tells

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  • Cal. 2236 runs at 28,800 bph and has a 55-hour power reserve. A movement running down in under 40 hours needs mainspring service.
  • The Siroui silicon spring is fragile; rough servicing can damage it. A conventional alloy spring in a stated 2236 movement indicates the spring has been replaced non-originally.
  • The oscillating weight is proportionally smaller than gents' Rolex movements; an oversized rotor indicates a caliber swap.
Sources: Rolex Lady-Datejust product page; RolexForums -- Lady-Datejust 279174 thread.

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