De Bethune

DB2109 Grand Bleu

Name: De Bethune DB2109 Grand Bleu DB2109
Brand: De Bethune
SKU: DB2109

Ref. DB2109

2019–present · 42mm · caliber De Bethune DB2109 (hand-wound, seconds tourbillon, 6-day power reserve)

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In-house manufacture caliber · caliber De Bethune DB2109 (hand-wound, seconds tourbillon, 6-day power reserve) · 144h power reserve (6 days)

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

The DB2109 tourbillon runs at the seconds and must complete exactly one rotation per minute; verify with a stopwatch.

Known issues in the market

Any variation outside one rotation per 60 seconds indicates a regulation issue requiring expert service.
The blued titanium dial shares characteristics with the DB28 KOB; verify it is the DB2109 reference by confirming the tourbillon placement.

Area	What to check	What is correct	Red flag
movement	Tourbillon rotation rate	Tourbillon cage completes exactly one rotation per 60 seconds	Rotation rate deviating from 60 seconds; regulation issue requiring service
dial	Blued titanium dial	Blued titanium dial with depth and variation consistent with controlled oxidation	Flat uniform blue; non-genuine dial substitution
caseback	DB2109 serial and documentation	Matching serial number and original De Bethune certificate	Missing or non-matching documentation; requires expert authentication

Common legitimate replacements

No common replacements; De Bethune parts are proprietary.

Expert resources: De Bethune directly; specialist independent watch authenticators.

Authentication guide

Last reviewed June 2026

The DB2109 Grand Bleu features a seconds tourbillon and a striking blue dial aesthetic. Caliber DB2109 in titanium or rose gold at 42mm. A tourbillon variant focused on the blue dial presentation and seconds indication through the tourbillon.

Known reproduction risks

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LOW

No known replica. The seconds tourbillon architecture with blue dial presentation is unique to De Bethune and cannot be approximated outside their production system.

Any claimed DB2109 with a non-blue dial is inconsistent with the Grand Bleu designation
Tourbillon that does not indicate seconds through cage position is mechanically different from the DB2109 specification

Introduced in 2019, the DB2109 is relatively recent; examples should have clear dealer provenance and minimal service history.

Dial variants by era

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Era	Description	Identifiers
2019 to present	Blue dial with no numerals; time reading via the tourbillon position as the seconds indication. The "Grand Bleu" name refers to the dominant blue aesthetic. Case in titanium or rose gold.	Blue dial with no traditional numerals Seconds tourbillon: the tourbillon cage position indicates the running seconds DB2109 designation on caseback 42mm case in titanium or rose gold Deep blue dial with minimal decoration

Service part flags

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Seconds tourbillon

Original: The seconds tourbillon uses the cage position around the dial to indicate running seconds in addition to its timekeeping function. The cage should complete one revolution per minute and be readable as the seconds indication.

Replacement tells

Tourbillon cage that does not have a seconds scale reference on the dial
Cage that does not complete exactly one revolution per minute

Case back markings

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2019 to present

DB2109 Grand Bleu designation
Individual serial number
Ti or 750RG material designation
30m water resistance

Movement tells

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The DB2109 caliber is the tourbillon variant with seconds indication through cage position; confirm the cage completes exactly one revolution per minute.
All De Bethune silicon escapement service notes apply; factory or authorized service only.
The blue dial is typically a treated or lacquered surface; inspect under magnification for any repair or touch-up to the dial surface.

Sources: De Bethune official.