Short answer
A fake Rotonde chronograph is a copy of the Cartier Rotonde de Cartier Chronograph. No copy carries the Cartier 1904-CH MC movement. Cartier does not sell that caliber loose, so every replica runs a third-party chronograph movement. The gap shows in the pusher feel, the reset action, and the caseback engraving.
Genuine reference points
The Rotonde de Cartier Chronograph uses caliber 1904-CH MC. It is automatic, with a column wheel and a vertical clutch. Cartier rates power reserve at 48 hours and frequency at 28,800 vibrations per hour. The steel version measures 40 mm across. Later and gold versions measure 42 mm. The crown holds a blue sapphire cabochon. The dial carries Roman numerals, a guilloché center, and a railroad minute track.
Movement checks
Ask for a photo of the movement through the caseback, plus a video of chronograph start, stop, and reset.
- Reset action. A vertical clutch lets the central seconds hand snap to zero from any position. Cam-actuated copies let the hand drift or lag.
- Pusher feel. The start pusher on a column wheel movement has short, clean travel. Copies feel soft or gritty.
- Sweep hand start. With a vertical clutch the hand starts without a jump. A stutter points to a modular or cam movement.
- Rotor and bridges. Genuine bridges carry Geneva stripes and Cartier engraving. Most copies show plain graining and no caliber number.
Case and dial checks
- Cabochon. Blue sapphire, domed, no flat top, no glue line at the seat.
- Dial print. The Cartier script and "Swiss Made" hold a sharp edge at 10x. Copy print thickens at the serifs.
- Guilloché. Genuine lines cut at even depth. Copy dials use stamped or printed patterns that flatten under raking light.
- Caseback. Reference and serial digits sit at even depth in the metal. On copies the digits sit shallow or on a sticker.
- Size. Measure the case with calipers and compare the result to the spec sheet for that reference.
Price and paperwork
A replica sells for a few hundred US dollars. A steel Rotonde chronograph on the secondary market costs far more, and that gap is the first test. Ask for the warranty card, the box, and a service record. A serial number that does not match the card is a stop sign. Selling a copy as genuine is a federal offense in the US under 18 U.S.C. 2320.
What stays unknown
Case thickness and reference numbers change by year and by market. Confirm both against the Cartier spec sheet for the exact reference before any purchase.