Answer first: the closest thing to a best replica of the Omega Speedmaster Grey Side of the Moon is a grey ceramic case build with a working chronograph, two subdials at 3 and 9, a date at 6, and a domed sapphire crystal with anti-reflective coating on both faces. Everything else, from the strap to the buckle, is a detail you can upgrade later. Judge any candidate on five criteria: case material and finish, chronograph function, dial print and hand geometry, crystal and tachymeter bezel, and strap and clasp. The sections below cover each one, with the trade-offs spelled out.

Case material and finish

The original Grey Side of the Moon is built around a 44.25 mm grey ceramic case with a brushed finish and a tachymeter bezel, and that material choice is the hardest thing for a replica to copy. A coated steel case can look right in photos and wrong on the wrist, because the finish sits on top of metal instead of being the metal.

  • Pros of a true ceramic case: the color runs through the material, so a chip does not expose bright steel; the surface holds a matte brushed texture; the weight and warmth feel close to the original.
  • Cons of a true ceramic case: ceramic can crack or shatter on a hard impact, it costs more, and fewer makers offer it in grey.
  • Pros of a coated steel case: lower cost, more resistance to everyday knocks, easier to find.
  • Cons of a coated steel case: a deep scratch reveals bare metal, case edges often look softer, and the finish tends to read glossier than the real thing.

Use-case recommendation: if you wear the watch daily and expect bumps, coated steel is the practical pick. If the goal is the look on the wrist from arm's length, hold out for ceramic.

Movement and chronograph function

The genuine watch runs the Omega Co-Axial calibre 9300, a column-wheel chronograph with two registers, a 60-minute counter and a 12-hour counter, plus a date at 6 o'clock. A replica either copies that layout and works, or it copies the look and does not.

  • Pros of a mechanical chronograph with a real column wheel or a close copy: firm pusher feel, the chronograph hand starts without a jump, and both counters advance as they should.
  • Cons: higher cost, harder to service, and water resistance that is rarely what a listing claims.
  • Pros of a quartz or decorative-subdial build: low cost, low upkeep, and often better timekeeping out of the box.
  • Cons: subdial hands that never move, a chronograph that resets oddly or not at all, and a pusher feel that gives the watch away in one touch.

Use-case recommendation: pay for a functional chronograph only if you will actually time things. If you want the look and nothing more, a quartz build costs less and avoids a service bill later.

Dial, hands, and date window

Expect a grey dial with two sunken registers, applied hour markers, polished hands with lume fill, and a date window at 6 that sits into the dial rather than floating above it. Photography hides a lot here, so compare print weight: cheap dials use heavy white print, an oversized logo, and the wrong font weight on the tachymeter text.

  • Pros of a well-finished dial: markers catch light the way applied metal should, the date sits centered in its window, and the two registers look the same depth.
  • Cons of a rough dial: flat printed markers, lume that is uneven or the wrong shade, a date wheel that is off-center, and subdial rings that are painted rather than recessed.

Use-case recommendation: ask for close-up photos of the dial at an angle before you commit. A dial problem is the one flaw you cannot fix with a strap swap.

Crystal and tachymeter bezel

The original uses a domed sapphire crystal with anti-reflective coating on both faces, which makes the dial nearly vanish at side angles. Budget builds use flat mineral glass or sapphire coated only on the inside, so the dial looks milky under indoor light. The tachymeter scale should be crisp, matte, and flush with the bezel surface, not a sticker sitting proud of it.

  • Pros of double-coated sapphire: clear dial at every angle, resistance to scuffs, and a domed profile that matches the case lines.
  • Cons: higher cost and coatings that can wear or flake over years of cleaning.
  • Pros of mineral glass: cheap and easy to replace.
  • Cons: scratches easily and reflects light hard, which flattens the dial.

Use-case recommendation: if you photograph your watches, double-coated sapphire is worth the premium. If the watch lives under a sleeve, mineral glass is an acceptable compromise.

Strap, buckle, and case back

The real watch ships on a grey leather strap with a ceramic deployant clasp. Replicas usually arrive on a leather strap with a steel clasp, sometimes with the wrong buckle shape or stitching color.

  • Pros of a good strap and clasp: correct grey tone, tight stitching, a clasp that closes with a solid click, and no sharp edges on the inside of the buckle.
  • Cons: strap quality is the first place makers cut corners, and a stiff or shiny strap is an instant tell.
  • Pros of a display case back: you can check the movement and rotor engraving yourself.
  • Cons: a decorated rotor on a basic movement looks busy rather than convincing, and printed markings are often shallow.

Use-case recommendation: budget for a replacement strap from the start. A better strap changes the whole watch, and it is the cheapest upgrade you can make.

Red flags to check before you buy

  1. Subdial hands that do not move when the chronograph runs.
  2. A pusher that needs a hard press or sticks on release.
  3. Case back markings that are painted rather than engraved.
  4. Seller photos that only show one angle, or a stock image rather than the actual watch.
  5. Claims of water resistance with no testing behind them.
  6. A price that is far below every other listing for the same build.

Ask for a short video with the chronograph starting, stopping, and resetting. That single clip answers more questions than a page of specifications.

Which build fits which buyer

Everyday wearer

Choose coated steel with a quartz or basic automatic movement. You get the silhouette, you worry less about damage, and upkeep stays simple.

Collector of replica builds

Choose the grey ceramic case with a functional chronograph and double-coated sapphire. This build costs the most and looks the closest, and it holds up to close inspection from a friend at dinner.

Occasional wearer

Choose a mid-tier build and put the savings into a proper strap. The strap and clasp sit in plain view, so money spent there shows more than money spent on a decorated rotor.

Legal and practical notes

Counterfeit watches infringe Omega's trademarks, and importing one into the United States can result in seizure by Customs and Border Protection. In practice that means a parcel can be stopped and destroyed with no refund. Beyond the legal side, keep two rules: never sell or trade a replica as a genuine watch, and never send one to an authorized service center, because it will be refused or held. Repair access is limited to independent watchmakers, so factor that into what you pay. If you want the real Grey Side of the Moon, buy from an authorized dealer or a documented secondhand listing and confirm the reference and papers before money changes hands.