40 mm case. Wears confidently on average to larger wrists. May overhang on slender builds.
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The De Ville Tresor uses a manual-wind Cal. 8912 with no automatic rotor; any Tresor caseback showing a rotor has a movement swap and is a disqualifying find.
Known issues in the market
Movement swaps to automatic Cal. 8500 or similar are the primary fraud vector; the Tresor caseback must show no rotor.
Cal. 8912 is METAS-certified; the METAS stamp must appear on the caseback alongside the Master Chronometer designation.
The small winding crown at 3 is the only crown; any Tresor with a crown at 9 or additional crown positions is incorrect.
Area
What to check
What is correct
Red flag
caseback
Manual-wind movement, no rotor
Cal. 8912 manual-wind movement visible through caseback with no automatic rotor present
Any rotor visible through the caseback; a rotor indicates an automatic movement swap
caseback
METAS certification stamp
METAS logo and Master Chronometer designation engraved on caseback
No METAS stamp; caseback with only COSC or no certification mark
crown
Crown position and function
Single winding crown at 3, winds the mainspring with smooth increasing resistance, no crown at 9
Authentication guide
Last reviewed June 2026
The De Ville Trésor is Omega's ultra-thin dress watch at 8.35mm case height, using the manual-wind cal. 8912 Co-Axial Master Chronometer. Roman numeral dial with no date. The extreme thinness is the defining characteristic -- any watch at this price point claiming to be a Trésor should have the case height measured against specification.
Known reproduction risks
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LOW
Case height not matching the 8.35mm specification
Case appears thicker than ultra-thin specification when viewed from the side
Caliper measurement shows case height significantly above 8.35mm
The De Ville Trésor is not a high-volume fake target. The ultra-thin case height is a measurable specification -- a simple caliper eliminates most case-thickness concerns.
LOW
Automatic movement substituted for manual-wind
Watch winds automatically without crown engagement -- the Trésor is manual-wind only
Crown at 3 o'clock does not advance a mainspring progressively when turned
Crown at 9 position; any crown layout other than single crown at 3
Common legitimate replacements
Manual-wind movements are occasionally swapped to automatic movements on serviced examples; caseback inspection is mandatory.
The slim profile of the Tresor is incompatible with most aftermarket straps; confirm the strap is sized correctly for the Tresor lug width.
Expert resources: Omega.com De Ville Tresor documentation. Omega Forums for Cal. 8912 manual-wind identification and METAS caseback stamp comparison.
Era
Description
Identifiers
2017 to present (cal. 8912)
Slim 40mm round case at 8.35mm height. Roman numeral dial in silver, champagne, or black. Leaf-style hands. Leather strap only -- no bracelet option on the standard Trésor. Manual-wind only. The ultra-thin profile is the defining design statement.
Roman numeral chapter ring -- same as the heritage dress watch tradition
Leaf-shaped hour and minute hands
Ultra-thin case: 8.35mm height, measurable with a simple caliper
No date window -- the Trésor is time-only
Leather strap only -- no bracelet
"Co-Axial Master Chronometer" and "Manual Wind" designation on dial or caseback
Service part flags
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Case height
Original: The 8.35mm case height is a measurable specification. An ultra-thin watch at this price point claiming to be a Trésor should measure within normal manufacturing tolerance of 8.35mm. A case that measures significantly thicker has either had components replaced or is not the stated reference.
Replacement tells
Case height measurably thicker than 8.35mm when measured at the case band with calipers
Case profile appears chunky or non-thin when compared to published reference images
Caliber 8912
Original: Cal. 8912 is manual-wind, Co-Axial Master Chronometer, with a 60-hour power reserve at 25,200bph. The caliber is exceptionally thin at 3.98mm. Manual winding via the crown at 3 o'clock with progressive resistance.
Replacement tells
Crown turns with no progressive resistance from a run-down state -- a manual movement with a broken mainspring or ratchet
Watch winds automatically -- the Trésor cal. 8912 is manual-wind only
Caseback shows a different caliber number than 8912
Leaf hands
Original: Leaf-shaped hour and minute hands -- wide at the pivot, tapering to a point. Polished to a mirror finish. The hand finish should be consistent with the case finish.
Replacement tells
Baton or dauphine hands where leaf hands should be -- indicates a hand swap
Hand finish matte where mirror is expected
Hand geometry inconsistent with the specific leaf profile for this reference
Case back markings
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2017 to present
Caliber 8912 designation
"CO-AXIAL MASTER CHRONOMETER" text
"30 M / 100 FT" water resistance
Case reference and serial number
"OMEGA" and "SWISS MADE"
Solid caseback with engraved decoration on some variants
Movement tells
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Cal. 8912 is manual-wind -- wind progressively from a run-down state and confirm resistance builds correctly. Full winding should feel firm. Power reserve is 60 hours from a fully wound state.
At 25,200bph the seconds hand has a smooth sweep. The ultra-thin case means the movement is extremely sensitive to shock. A watch that has been dropped may show timekeeping irregularity without visible case damage.
The Co-Axial escapement in an ultra-thin manual-wind is a technically complex achievement. Any service should be performed by a watchmaker with Omega movement training -- thin movements are more prone to damage from incorrect tool use.
