Short answer

A fake Omega Speedmaster Gray Side of the Moon is a replica of reference 311.93.44.51.99.001, a 44.25mm chronograph with a grey ceramic case and a sandblasted grey dial. Replicas sit in two rough buckets: budget builds under about $150 that use coated steel and a basic movement, and higher tier builds in the $300 to $600 range that imitate the ceramic look and copy the two subdial layout. Neither one is ceramic through the whole case, and the movement is where the difference shows first. Once you know which parts are copied and which are approximated, you can read a listing in about two minutes.

What the genuine watch is

The Grey Side of the Moon was Omega's follow up to the Dark Side of the Moon, swapping black ceramic for a grey zirconium oxide ceramic case. The material is colored through, so a scratch stays grey instead of exposing metal underneath. The dial carries a fine sandblasted texture that shifts as light moves across it, the subdials sit at 3 and 9, and the date window sits at 6. Inside is the caliber 9300, an automatic co-axial chronograph with a column wheel and a silicon balance spring. Confirm the current spec sheet on Omega's own site before you compare anything, because small details changed across production.

The tells that matter

Case material

This is the first thing I look at. Genuine grey ceramic has depth, it looks like a solid block of grey rather than a painted surface, and the polished flanks stay free of hairline scratches after months of wear. A coated steel replica picks up fine scratches on the polished areas, and at the lug edges or crown guards you can often find a tiny chip where the coating flaked and silver steel shows through. A magnet will not help you here, since the movement inside is steel on both watches.

Weight and thickness

Ceramic is lighter than steel of the same volume, so a real one feels lighter in the hand than its size suggests. Coated steel replicas feel denser and sometimes feel colder for longer. Thickness is another gap. Compare the case against published dimensions rather than against photos, because listing photos are usually shot at an angle that hides a thin or fat profile.

Dial, hands, and lume

The sandblasted grain is hard to fake. Replicas usually use a flat printed dial, or a texture that is too coarse and reads like sandpaper up close. Check the distance from the subdial centers to the center of the dial, since replicas often place them a millimeter or two off. Look at the date window cut, the shape of the hands, and the lume. Charge it with a phone light and compare the glow: a greenish or bluish glow against the original pale tone is a giveaway.

Movement and pushers

Real caliber 9300 has two subdials, one counting chronograph hours and minutes at 3 and running seconds at 9. Most replicas run an Asian 7750 variant or a decorated automatic with a faux chronograph layout. Press the pushers. A column wheel chronograph has a crisp, short action with no mush and no click that feels like a cheap ballpoint pen. Start the chronograph and watch the central seconds hand. It should move smoothly, stop cleanly, and reset to zero in one snap. Then check that the 3 o'clock subdial actually counts hours and minutes and that the 9 o'clock subdial runs all the time as running seconds. On many fakes one of those is decorative.

Caseback and engraving

The genuine watch has a sapphire display back. Look at the rotor and bridge engraving. Wrong font, missing silicon balance markings, or sloppy text spacing all point to a low tier build. A rotor that rattles or spins loosely when you tilt the watch is another sign.

What to verify before you pay

  • Ask for a photo of the case edge in direct sunlight, not a studio shot with soft light.
  • Ask for a short video with the chronograph running, started and stopped twice.
  • Ask for the exact case diameter and thickness with calipers in the frame.
  • Ask which movement is inside, by name, not by the phrase "high grade automatic."
  • Ask whether the date flips at midnight or drifts over several hours.
  • Ask about water resistance claims and treat any answer above splash resistance as marketing.
  • Ask the return window and whether returns are accepted for movement faults.
  • Check the strap or bracelet against the configuration you are told it matches.

Realistic expectations

No replica of this reference will pass a service desk inspection. The ceramic case and the 9300 architecture are the two most expensive things to copy, and they are the two things replicas get closest to, not exact. Buy on the look and the fit, not on resale value. Plan for service, since chronograph movements need attention, and a local independent watchmaker may or may not work on clone calibers. Keep it away from water and from drops, because a ceramic case cracks rather than dents, and a cracked replica case is not repairable.