Quick answer
Cartier does not list a 24mm Ballon Bleu. The smallest Ballon Bleu de Cartier in the current catalog is 28mm. A "fake Ballon Bleu 24mm" is a seller label for a small quartz copy that measures 24mm to 25mm across the case, or a mislabeled 28mm replica. Measure the case before you pay.
Case size and measurement
Case size is the diameter at the 3 to 9 o'clock line. Crown and lugs are not part of that number. A genuine 28mm Ballon Bleu reads 28mm on that line. Many listings that say 24mm measure 25mm or 26mm. Ask the seller for a caliper photo on the case. A dial photo next to a ruler proves nothing.
Movement
Small Ballon Bleu cases run quartz. The genuine 28mm Ballon Bleu is quartz. Replicas use a Swiss Ronda, an ETA quartz caliber, or a Japanese Miyota. Quartz keeps the case thin. Most 24mm to 28mm quartz copies land between 7mm and 8mm thick. An automatic movement in a 24mm case adds 2mm to 3mm of height and raises the crown. A seller who calls a 24mm case "automatic Swiss" should show the rotor through the caseback.
Crown and cabochon
The genuine crown is fluted steel with a blue synthetic spinel cabochon. The stone is not sapphire. It is a polished dome with a deep blue tone. Replica cabochons are plastic, glass, or dyed quartz. Plastic shows a seam on the side and scratches with a fingernail.
Dial and crystal
The dial carries Roman numerals, a guilloche pattern, and blued steel sword hands. Cartier sets a secret signature inside the VII numeral. Genuine crystals are sapphire. Mineral glass on replicas scratches and reflects light with a softer edge. Some sizes show a date at 3 o'clock and some do not. Match the dial layout to the reference number, not to a stock photo.
Price
Prices for 24mm to 28mm quartz replicas run $40 to $250. Movement and case finish drive the spread. A sapphire crystal and a steel bracelet push the top of the range. Photos of the movement, crown, and caseback tell you more than a written description.
Legal risk in the US
Importing a counterfeit watch into the United States is illegal. CBP seizes counterfeit goods at the border. Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320, with a maximum of 10 years for a first offense. A purchase from an overseas seller can end with a seizure notice and no watch.
Checks before buying
- Get a caliper photo at the 3 to 9 o'clock line.
- Get a daylight photo of the crown and cabochon.
- Ask which movement the case holds and for a caseback photo.
- Compare the dial layout with the Cartier reference number.
- Get the return policy in writing.