Short answer

Reference 424.10.40.20.02.001 is a 40mm stainless steel Omega De Ville Trésor with a silver opaline dial and a Master Co-Axial automatic movement. Fakes of this exact reference exist, but the Trésor is not a high-volume target the way the Speedmaster or Seamaster is. Much of what gets sold as a "Trésor" is really a generic 40mm dress watch with a reprinted dial and a Trésor name on the rotor. If you want one detail that settles the question quickly, look through the sapphire caseback: you will not find a real Co-Axial escapement, a silicon balance spring, and a free-sprung balance in a counterfeit.

What the real watch is

Omega brought the Trésor name back in 2014 as part of a slimmer, dressier De Ville line. The steel version uses a 40mm case with flat brushed flanks and polished bevels, a thin bezel, and sapphire on both faces. The dial is what Omega calls opaline silver, a soft satin finish that shifts from pale grey to warm white as the light moves across it. Markers are applied and faceted, hands are thin and polished, and the minute track is printed rather than applied.

Inside sits a Master Co-Axial automatic from the 8500 family, with twin barrels, a rated anti-magnetic resistance of 15,000 gauss, and a 60-hour power reserve. That movement is the reason the caseback is sapphire instead of solid steel, and it is also the reason fakes struggle.

Where fakes give themselves away

Case and lugs

Real Trésor lugs have a crisp line where the brushed top facet meets the polished side. Fakes usually round that transition off because it takes extra hand work to keep it sharp. Run a fingernail along the lug edge. On the real thing you feel a defined ridge. On a fake you feel a rolled-over curve.

The dial finish

Opaline is not a flat silver paint. It has a fine grain that diffuses light without glare. Fake dials tend to be either chalky and flat or too glossy, and the printing often sits slightly heavy under a loupe. Look at the applied markers: on the real watch each one is polished on every visible face and sits square to the dial. On a fake the marker edges look stamped, the polishing is uneven, and the feet sometimes cast a shadow because the marker is not seated flush.

Crystal and anti-reflective coating

Omega treats both faces of the crystal. A fake usually has coating on the inside only, which shows up as a grey or blue wash across the dial at an angle, plus reflections that the original does not produce.

Caseback, engraving, and the movement window

Engraving on a real caseback is deep and crisp, and the reference and serial are struck, not laser-etched with a light touch. Open the caseback view and look at the rotor: a real 8500-family rotor carries fine arabesque striping, blackened screws, and engraving that matches the stated jewel count. Fakes run a Miyota 9015, a Seagull, or a Chinese copy of an ETA. Beat rate is not a tell here, since most of those run at 28,800 vibrations per hour like the original. What is a tell is a regulator arm and a conventional balance wheel.

Papers, cards, and numbers that should match

A complete set includes a pictograms card and a warranty card, and the reference and serial on those cards should match the case and the movement number visible through the caseback. Fakes often ship with cards printed in the wrong font, with numbers that do not line up, and with a manual that belongs to a different model. If a seller refuses photos of the movement number, stop there.

What is actually at risk

Three real costs. Omega will not service a counterfeit, and independent watchmakers cannot get parts for one, so a broken fake becomes a paperweight. Resale value is effectively zero. And in the United States, Customs and Border Protection seizes counterfeit watches at the border, which means the money is gone and the watch never arrives.

Checks I would run before paying

  • Ask for a straight-on photo of the dial and one at 45 degrees to judge the opaline finish.
  • Ask for a photo of the movement through the caseback, in focus and well lit.
  • Confirm the reference appears in full somewhere other than a search title.
  • Compare lug finishing against a photo from an authorized dealer listing.
  • Check that the serial on the card matches the movement number.
  • Price it against recent sold listings. A steel Trésor trades in the low thousands used, and anything far under that is a different watch than the one advertised.

If you just want the look

The Trésor is a thin, plain, two-hand-plus-dial dress watch. That shape is not exclusive to Omega. A vintage De Ville from the 1960s, a Nomos Tangente, or a Junghans Max Bill all deliver the same visual idea with a real movement, real service support, and value that holds. That is the version I would put on my wrist.