The short answer
A replica Calibre de Cartier 42mm is a counterfeit copy of the steel automatic Cartier launched in 2010 to showcase its first fully in-house movement, the 1904-PS MC. The genuine watch is 42mm across, about 11mm thick, wears a date at 3 o'clock, and carries a 48-hour power reserve. Copies in this size usually nail the diameter and miss on thickness, dial texture, and the movement you see through the back. If you want one honest shortcut for judging these things: flip it over first. The caseback tells you more than the dial does.
What the real 42mm actually is
Cartier built the Calibre line around a case with a wide, flat bezel and a dial with an oversized Roman XII at the top and a subdivided outer track. The stainless steel 42mm reference runs roughly 11mm thick, which matters because that number is hard to fake. The 1904-PS MC inside is a 27-jewel automatic with a bidirectional winding system, 48 hours of running time, and a date corrector you reach through the crown. It is finished with Geneva stripes and Cartier's own engraving, and it is visible through a sapphire exhibition back.
Where the copies drift
The first thing I measure is case thickness. Most replicas land between 12mm and 13.5mm because the movements inside are not the same footprint as the 1904-PS MC, and no amount of good machining hides 2mm. The second is the dial's flinqué texture, the faint concentric guilloché pattern. Real ones catch light in a clean swirl. Replicas either stamp it shallow or omit it and print a flat surface.
After that, check the crown. The genuine crown carries a blue synthetic spinel cabochon, and the color is a deep, slightly grey blue, not a candy blue. Look at the date window too. Cartier's date font is narrow with a distinctive 4 and a clean 1. Copies tend to use a fatter, more generic font and a date wheel that sits slightly off-center.
The tells I check first
- Thickness measured with calipers, not eyeballed
- Print sharpness on the Roman numerals and the "Swiss Made" line at 6
- Alignment of the small outer track to the indices
- Caseback engraving depth and whether the reference numbers match the dial variant
- Crown cabochon color under natural light
- Rotor noise and winding feel, which on cheap movements is loud and gritty
- Lug finishing, where real Cartier polishes and brushes on a hard line
Movements you will find inside
This is where the money actually goes. Lower-tier copies run a basic 21,600 vph Asian automatic with a printed rotor plate that pretends to be a 1904-PS MC. Mid-tier units use a Miyota 9015 or a Seagull ST21, both decent timekeepers in their own right but with different beat rates and rotor shapes than the Cartier caliber. The upper tier tries to pass off a decorated clone with Cartier engraving. None of them share parts with the real movement, which means no Cartier service center will touch one, and any independent watchmaker will bill you for whatever generic parts they can source.
Water resistance and daily wear
The genuine 42mm is rated to 30 meters, which is splash protection, nothing more. Replicas often claim 30 or 50 meters on the caseback with no gasket testing behind the claim. I would not swim in either one. If you own a copy, get it pressure tested before it goes anywhere near a pool, and expect a watchmaker to decline the test if the caseback gaskets are glued rather than seated.
The legal side, plainly
In the United States, trafficking in counterfeit goods is illegal under 18 U.S.C. 2320, and U.S. Customs and Border Protection treats counterfeit watches as prohibited merchandise subject to seizure and destruction. There is no personal-use exemption that makes import safe. Buying one from an overseas seller can mean a seizure notice, a lost payment, and no recourse. That is a real cost on top of the watch.