The short answer first: on an Omega Constellation from the 123.10 family, four things expose almost every fake. The four griffes, the claws on the bezel at 3 and 9, the way the integrated bracelet meets the case, the stamped Observatory medallion on the back, and the beat of the movement. Check those in order and you filter out the great majority of counterfeits before you ever open the case.
What ref 123.10 actually is
The 123.10 group is a mid-2010s steel Constellation. Omega's reference system for that era reads like this: 123 is the Constellation family, 10 means stainless steel, the next two digits are the case diameter in millimeters, and the final block covers the dial and movement combination. So 123.10.35.20.01.001 is a 35mm steel Constellation with the co-axial calibre 2500 and a silver dial. The same family covers 24mm and 27mm quartz pieces for smaller wrists, plus 38mm automatics, and those larger versions use a different movement. Match the watch against the exact variant before you apply any test. A 35mm case with a quartz movement is not a variant, it is a fake.
The griffes are the first thing I look at
Two pairs of machined steel claws sit on the bezel at 3 and 9, and they are the hardest part of the design to copy at low cost. On a genuine watch they are sharp-edged, with a visible bevel along the top face, and they blend into the bezel instead of sitting on top of it. The inner faces are flat and clean. On fakes they tend to be thicker, rounded at the tip, or cast in one piece with the bezel so the line between claw and bezel disappears. Run a fingernail along the joint. Real ones catch. Fakes feel like one smooth lump.
Case, crown, and crystal
The steel 123.10 cases are slim for their size, roughly 10.5mm thick at 35mm across. Fakes add a millimeter or more because the movement inside is a generic one. The crown is signed, correctly fluted, and sits close to the case band; a fatter crown with a mushy logo is a bad sign. The crystal is domed sapphire with anti-reflective coating on the inside face, so it reads nearly invisible from most angles. Mineral glass on a fake shows a green edge tint and a harder reflection you can spot from across a table.
Flip the watch over and look between the lugs at 12. The full reference number, 123.10.35.20.01.001 in that example, is laser engraved into the case. It should be thin, even, and readable under a loupe. Many fakes have nothing there, or the wrong digits, or a number that belongs to a different case size.
Dial and hands
Omega puts a lot on a small area. The symbol at 12 is applied metal, not paint, and the wordmark under it is thin and even. The star that belongs with the Constellation name is a separate applied element on most dials. SWISS MADE at 6 sits in two halves, one on each side of the marker, in type you can read under magnification. Fakes smear it or run it as one line.
Hands are faceted with polished flanks and a bevel that catches light along its length. Fake hands look flat, sit slightly too thick, and end in blunt tips. Lume varies by dial variant, so do not use it as a main test. Check the date window instead. The aperture should be centered on its axis, with machined inner edges and no gap between the dial cut and the frame.
Bracelet and clasp
The bracelet is integrated, which means no spring bar gap at the lugs. End links sit flush against the case with no step, no wobble, and no daylight showing through. Links flex without rattle. The clasp is where fakes get lazy. Look for a crisp Omega symbol, clean STAINLESS STEEL stamping, and a folding mechanism that closes with a firm click and sits flush when shut. Rough stamping, a thin clasp body, or a lid that stands proud when closed all point the same direction.
Caseback and movement
Most steel 123.10 watches have a solid caseback with the stamped Observatory of Geneva medallion and its ring of stars. Genuine stamping is deep and crisp under a loupe. Fakes are shallow, blurry, or carry the wrong star count. A few later 38mm pieces show the movement through sapphire, so confirm the exact reference before you treat a display back as proof of anything.
For the 35mm automatic, the calibre 2500 runs at 25,200 vibrations per hour, which is 3.5 Hz and seven beats per second, with about 48 hours of power reserve. A quartz tick in a 35mm case is wrong. A movement beating at 28,800 is not a 2500 either. A watchmaker with a timing machine settles this in under a minute, and it is the cheapest test you can buy.
Fast checks while it is in your hand
- Weigh it. Thin fakes feel light for their size, and a top-heavy bracelet feels wrong on the wrist.
- Measure the case. 24, 27, 31, 35, and 38mm are the sizes that belong to this family.
- Loupe the reference engraving between the lugs.
- Watch the second hand sweep for ten seconds.
- Wind it and set the date. Real movements feel crisp; cheap ones feel gritty.
Where fakes slip most often
- Claws that are rounded, glued, or cast with the bezel.
- End links that leave a visible gap at the case.
- A flat or shallow caseback medallion.
- Printed logos where applied metal belongs.
- A case that is a millimeter too thick.
- No reference number, or one that does not match the size on the wrist.
Before you pay
Compare the watch against the exact reference photo on the maker's site, not against a search result that might itself be a fake. Ask for photos of the caseback, the clasp, and the reference engraving, plus a timegrapher reading. A price far below the used market for that reference is the oldest signal there is. If you are buying second hand, have an independent watchmaker look at it before the return window closes.
One last distinction worth keeping straight. A replica sold openly as a replica is a different product from a counterfeit sold as a genuine Omega. This guide is about catching the second kind, the one that takes your money and leaves you with a watch that fails every test above.