Short answer
A two-tone Clé de Cartier pairs a steel case with 18k yellow or rose gold parts. Copies match the outline. They fail on four points: gold content, crown shape, dial print, and weight.
The genuine model
Cartier launched the Clé de Cartier in 2015. "Clé" is French for key. The crown at 3 o'clock is shaped like a key head and set with a sapphire cabochon. The case is a rounded square.
Two-tone versions come in 31mm, 35mm and 40mm. Bracelet versions mix polished steel centre links with gold outer links. The clasp carries the Cartier name. Gold parts are 18k and marked 750. On a two-tone bracelet the gold is solid, not plated.
Casebacks carry a reference number, a serial number and Swiss assay marks.
Checks that catch most fakes
- Weight. A 35mm two-tone on a full bracelet runs over 100 g. Copies run lighter.
- Gold marks. Check the caseback and the clasp. Real gold parts show 750 plus an assay stamp. Copies show plating or nothing.
- Crown. The key head has flat facets and a narrow shaft. Copies show a soft rounded knob and a cabochon that sits too large, too blue, or proud of the metal.
- Dial. Roman numerals sit on a silvered opaline ground. Print edges stay sharp at 10x magnification. The date window, when present, is cut square with a bevelled frame.
- Hands. Blued steel on many references, with a polished bevel under raking light. Copies show flat painted blue.
- Bracelet screws. Heads sit flush and slot depth is even. Copies show chewed slots and proud heads.
- Serial and reference. Fakes repeat the same numbers across batches. Cartier records are the only confirmation.
Movement note
Cartier fits the in-house 1847 MC automatic in the 35mm and 40mm Clé. The 31mm runs on quartz in most references. Caseback style differs by reference. Confirm against the reference number, not against photos alone.
Where to verify
Cartier boutiques and authorised service centres inspect a watch on request. A box with the matching reference and a serial that lines up helps. Paper alone does not prove a watch. Sales listings that hide the caseback or the clasp photo are a warning sign.