Short answer

The "151" in a listing is a batch or version code used by replica sellers, not an Omega reference number. A fake Constellation Master Chronometer 151 is a replica of Omega's modern Constellation line, built around a Chinese automatic movement dressed up to look like a Co-Axial caliber. On a phone screen it reads well. On a wrist, and on a timegrapher, the gaps show up fast.

The important part: no replica carries Master Chronometer certification. That label belongs to METAS, and it applies to the fully cased watch after eight separate tests. Nobody is sending a $300 replica to Switzerland for that.

What the genuine watch actually is

Omega's Constellation goes back to 1952 and has been through dozens of generations. The modern versions use Master Chronometer movements, which means the finished watch passed METAS testing for accuracy of 0/+5 seconds a day, magnetic resistance to 15,000 gauss, and water resistance at the rated depth. The Globemaster was the first model to carry that certification, and the Constellation family followed.

That matters here because it tells you what the replica is imitating and where the imitation has to fail. A certified watch is certified as a whole unit. A replica is a case, a dial, and whatever movement the factory could buy that week.

Movement: where the money goes

I look at the movement before anything else, because it decides whether the watch runs for a year or a month. Most replicas in this tier use a decorated automatic, often a Miyota-style or a Chinese clone with a fake rotor engraving and cosmetic Geneva stripes.

• Ask which movement is inside, and be suspicious of vague answers like "Japanese movement" with no model name.
• Look at the rotor engraving under a loupe. If the lettering is soft or uneven, the decoration is stamped, not engraved.
• Check the beat rate. Genuine Master Chronometer calibers run at 25,200 vph. A replica at 21,600 tells you it is a different architecture entirely.
• Wind it by hand. Gritty feedback or a crown that feels loose is a cheap keyless works, and that is a repair waiting to happen.

Dial, hands, and the star

The Constellation dial has a lot of small tells. Applied indices should sit flat and even, with polished edges that catch light the same way across the whole dial. Print should be crisp at the edges, not fuzzy or doubled. The star above the logo is a common weak point in replicas: it comes out thick, off center, or with uneven points.

Hands are the other giveaway. Dauphine and alpha hands need sharp, straight facets running down the center. On replicas those facets often disappear under reflection, or the hands are slightly too short and stop before the minute track.

Case, claws, and bezel

The Constellation's signature is the pair of polished claws on either side of the case at 3 and 9. On the real thing they are milled as part of the case and blended into the flanks with a soft transition. On a replica they are usually pressed or glued on, and the seam shows when you run a fingernail along the edge.

Check the bezel too. If it is supposed to be a fluted or Roman-numeral engraved bezel, the cuts should be sharp and evenly spaced. Replica engraving tends to be shallow and slightly wavy.

Bracelet and clasp

This is where most buyers notice quality first. Links should articulate with no rattle and no tight spots. The clasp should close with a firm, single click. Look at the end links where they meet the case: on a good replica they hug the lugs with a small, even gap. On a bad one there is daylight on one side and contact on the other.

What no replica gets right

• METAS certification and the paperwork that goes with it. Any card in the box is decorative.
• 15,000 gauss magnetic resistance, which needs specific alloys and a silicon escapement.
• Case finishing at the level of a Swiss factory, particularly the polish on the claws and the brushing on the flanks.
• Service support. Genuine Omega service centers will not touch a counterfeit, and most independent watchmakers will not either.

Price and red flags

Expect a few hundred dollars for the tier usually sold as "151," and treat anything below that as a disposable. Red flags include stock photos with no real-world shots, sellers who claim METAS certification, and listings that mix photos of two different watches in one gallery.

Also remember the legal side. A counterfeit is a trademark-infringing product. You can own one in most countries, but you cannot resell it as genuine, and customs can seize it in transit. Buy with that in mind and you will not be surprised.

Bottom line

A fake Constellation Master Chronometer 151 can look convincing in a photo and decent on a wrist for a while. Judge it as a replica, not as an Omega. Look at the movement first, the case finish second, and ignore any certificate in the box.