A real Cartier watch will have a serial number engraved and not etched. A counterfeiter will often have a fake serial number etched into the back of the watch. The serial number will consist of two letters and six digits.
Unfortunately, there is no online tool to check if the serial number is genuine. You will have to contact a Cartier services department directly. However, one thing you should know is that an authentic Cartier watch will come with a certificate that will have the serial number on it. So, check the certificate matches the serial number on the watch before making your investment.
Whether to exploit legal loopholes or simply because of translation issues, the spelling on a fake Cartier is often wrong. The most common difference is the removal of the first R (so it reads Catier). The name is always engraved on the back of the watch with the correct spelling and serial number.
For convenience sake, most watch brands stamp the serial number on the exterior of the watch for easier identification. Take your watch off and take a look at the back. You will more likely than not find the manufacturer, model number, country of origin, and serial number engraved. 2b1af7f3a8