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Movement tier: unclassified · caliber Montblanc Cal. MB 29.21: in-house automatic with moon phase and date, 28,800bph, 42h PR; used in Star Legacy Moonphase; Montblanc Swiss manufacture caliber · 42h power reserve
Medium-large: suits wrists 6.5 in+ (16.5 cm+)
42 mm case. Wears confidently on average to larger wrists. May overhang on slender builds.

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Authentication

Dress watch with moon phase; the polished case must be in factory condition and the moon disc must show correct phase.

Known issues in the market
  • The moonphase disc must reflect the correct current lunar phase; verifying against a lunar calendar confirms the disc is set and functioning correctly.
  • The Star Legacy is a dress watch; case polishing removes original surface character and is a quality concern at this level.
AreaWhat to checkWhat is correctRed flag
dialMoon phase accuracyMoon disc shows correct lunar phase relative to actual moon; setting confirmed via lunar calendarIncorrect lunar phase; moon disc not set or moon mechanism not advancing
caseCase finish conditionPolished case in factory condition; no over-polishing or re-polishingOver-polished case; case re-polished removing original surface character
casebackCal. MB 29.21 movementMB 29.21 with moon phase module visible through caseback; Minerva-heritage finishingNon-in-house movement; movement swap
Common legitimate replacements
  • Leather strap; Montblanc OEM.
  • Crystal; sapphire standard.
Expert resources: Montblanc Star Legacy Moonphase product documentation; Montblanc authorized service.

Authentication guide

Last reviewed June 2026

The Star Legacy Moonphase uses the MB 29.21 manufacture caliber; the Roman numeral dress dial, moonphase aperture at 6 o'clock, and Montblanc star finishing are the authentication anchors.

Known reproduction risks

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LOW

The Star Legacy is a dress moonphase reference; not a significant reproduction target.

  • Applied Roman numeral quality under 10x magnification.
  • Moonphase disc printing; moon body three-dimensionality.
  • MB 29.21 Montblanc-signed rotor through caseback.

Dial variants by era

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EraDescriptionIdentifiers
2018 to presentSilver or blue dial with Roman numerals; moonphase aperture at 6 o'clock; date window; 42mm case.
  • STAR LEGACY on dial
  • MB 29.21 on caseback
  • Roman numeral chapter ring
  • Moonphase at 6 o'clock
  • Date window at 3 o'clock

Service part flags

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Moonphase disc

Original: Deep blue disc with gold-tone moon and stars; crisp engraving or printing.

Replacement tells
  • Moon body that appears flat or printed rather than three-dimensional.
  • Star field that is blurred or pixelated under magnification.
Roman numerals

Original: Applied Roman numerals raised from the dial surface; polished finish.

Replacement tells
  • Printed Roman numerals in place of applied indicate a non-original dial.

Case back markings

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2018 to present
  • MONTBLANC STAR LEGACY
  • MB 29.21 caliber designation
  • SWISS MADE
  • 30M WATER RESISTANT
  • Display caseback standard

Movement tells

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  • The MB 29.21 is a Montblanc manufacture automatic with moonphase; the rotor should carry the Montblanc star and brand.
  • Moonphase accuracy: the disc advances by one tooth per day; a moon that is off by several days has either skipped or was misset at service.
  • At 30m water resistance, this is a dress watch; avoid water exposure.
Sources: Montblanc Star Legacy Moonphase.

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