Short answer
A good replica of the Omega Speedmaster Gray Side of the Moon is a 44.25 mm chronograph with a gray ceramic case, a two-register dial and the date at 6 o'clock. If the case is real ceramic and the dial layout matches, it holds up at arm's length. If the case is gray PVD-coated steel, it never will, no matter how clean the printing is. Case material is the first thing I check and the last thing most buyers ask about.
Why ceramic is the whole point
The genuine watch uses zirconium oxide ceramic for the case, the bezel and the caseback. It gets sintered at high heat, so it comes out lighter than steel and hard enough that daily knocks leave nothing behind. That hardness cuts both ways: ceramic does not bend, it chips or cracks, and there is no polishing a chip out.
The replica market handles this in three ways. Cheap versions use gray paint or PVD over a steel case. Mid-tier versions use a steel case with a ceramic bezel insert only. The better ones use a full ceramic or ceramic-composite case with the right satin finish. You can spot the difference by weight, by temperature (steel feels colder at first touch), and by the edges, where coated steel tends to show a thin line of bare gray steel over time.
Movement: what is actually inside
The genuine runs the Omega calibre 9300, an automatic chronograph with twin barrels, a 60-hour reserve and a silicon balance spring. Two subdials total: a combined 60-minute and 12-hour counter at 3, running seconds at 9, and the date at 6.
No replica at any price has a true 9300 clone. What you get is usually a modified 7750-family automatic with the date wheel shifted to 6 o'clock, or in the better builds a Chinese column-wheel chronograph. Both work. The 7750-based option is the more serviceable of the two and parts are common, but the relocated date mechanism is the weak spot, so change the date gently and stay out of the 9 pm to 3 am window.
Dial, hands and bezel
Four things are worth a close look:
- Subdial depth. On the real thing the counters sit in their own recessed rings. Flat printed subdials are the clearest tell.
- Applied markers. They should stand off the dial with polished sides, not sit flush against it.
- Bezel printing. The tachymeter scale on the ceramic bezel is crisp and matte with no bleed at the edges.
- Date window. It should be cut clean with no white halo around the disc.
Size and how it wears
44.25 mm across and about 16 mm thick on the genuine. That is a big watch, and the ceramic case makes it lighter than the numbers suggest. A steel replica of the same dimensions feels heavier and sits lower on the wrist. If your wrist is under roughly 6.75 inches, this reference will overhang, and no replica fixes that.
The genuine comes on a gray leather strap with a deployant clasp. On replicas the clasp is usually where the finish drops off fastest, so check the engraving and how the spring bars seat.
Checklist before you pay
- Ask what the case is made of, in writing. "Ceramic" and "ceramic-coated" are not the same answer.
- Ask for a photo of the caseback edge under daylight, where coating flaws show first.
- Confirm the movement family and whether the date is driven off the chronograph gear train.
- Check the pusher action. It should feel firm and consistent, not gritty or spongy.
- Verify the crown threads and how it seats against the case.
- Ask about crystal anti-reflective coating. A washed-out dial under indoor light means it is missing.
- Confirm water resistance claims in practice, not on paper.
Where replicas fall short
Lume is the usual weakness. Genuine hands and markers glow for hours, and most replicas fade in twenty minutes or glow a slightly green shade. Pusher feel is second. Third is the caseback, where the satin brushing on ceramic should be uniform and slightly matte rather than glossy. Fourth is the strap, which tends to be stiffer leather than the real thing and breaks in slowly.
Living with a ceramic case
Treat it like glass with a movement inside. Ceramic survives desk knocks and bracelet rubs, but a drop onto tile or a hit against a door handle can crack it, and a cracked case is a total loss. Skip the pool and the shower. Keep it away from abrasive cleaners, since the matte finish picks up oil from skin and needs only warm water and a soft cloth. Get the movement serviced every few years if you plan to run the chronograph often, because a dry 7750-based movement wears its pivots quickly.