Quick answer
On a replica calibre 42mm listing, 42mm is the case diameter across the widest point, measured without the crown. "Calibre" is the movement family name borrowed from the genuine watch. Those are two separate claims, and they fail separately. A seller can get the case right and the movement wrong, or the other way around. Read the spec sheet as if it were two products.
Where the phrase comes from
Cartier built a 42mm diver under the Calibre name, and that combination is what most buyers are searching for when they type "calibre 42mm." Other brands use Calibre for their own movements at other sizes, so the number and the name do not always travel together. If a listing pairs Calibre with 42mm and nothing else, ask which reference it is copying. A seller who cannot name the reference usually cannot name the movement either.
Movement wording, decoded
I look at the movement line first, because that is where the vague language hides. Common phrases mean different things:
- "Calibre 42" with no maker: usually a generic automatic, not a clone of anything specific.
- "Swiss movement" on a replica: often an ETA pattern or a close copy, occasionally a Swiss part set into an Asian build.
- "Japanese automatic": typically a Miyota or Seiko pattern, which tends to be reliable and cheap to service.
- "Decorated to match": the rotor and bridges are engraved to look correct through a display back. Check photos of the actual movement, not a stock render.
Why 42mm is the number to check twice
Diameter alone tells you less than sellers imply. Lug to lug and case thickness decide how a 42mm watch sits. A 42mm diver with 50mm lugs swallows a 6.5 inch wrist, while a thin 42mm dress case wears smaller than its measurement suggests. Replicas often run thicker than the original because the movement inside is not the same height. Ask for thickness in millimeters. If the seller quotes only "42mm," you have half a spec.
Case and dial details that expose a bad build
Look at crown guards, bezel action, and date window alignment. On a 42mm diver, the crown should sit flush with the guards and the bezel should click through defined positions, not spin loose. Date fonts are a common giveaway. So is a cyclops that distorts the number. These details matter more at 42mm than at 40mm because the extra surface area makes sloppy finishing easier to see.
Water resistance claims
Printed depth ratings on replicas are marketing, not test results. Genuine ratings come from standardized pressure testing. Unless a seller states that a watch was pressure tested and offers a number, treat any dive rating as splash resistance and keep it out of the pool.
My short checklist
- Confirm the reference being copied.
- Get diameter, lug to lug, and thickness.
- Ask which movement, by maker and model number.
- Request photos of the actual piece, including the caseback.
- Decide whether the movement is serviceable in your area before you pay.
A 42mm replica calibre can be a solid daily wearer. It just needs the two claims, size and movement, verified one at a time.