To identify the model of a Cartier watch, turn it over and place it on a clean, soft surface. On the back of the watch case are two series of numbers. The longer, eight-digit number with letters is the serial number of the watch. The four-digit number engraved on the back of the case is the model number. Use the model number to determine the model of the watch with the assistance of a reference book of Cartier watches.
Cartier watches models and model numbers are found in several reference books, including "Cartier - Watch Catalog." Some websites, such as Orbita.com, also list Cartier model and serial numbers that can help identify the watch.
The four-digit model number on the back of the case dictates the size and dimensions of the case, however, the materials can vary for different watches. Another unique model number is indicated only in the watch's paperwork. This number typically starts with a “W,” and is the same only for exact matches of the watch. Some older models and quartz watches don't have a model number on the back of the case. In such an instance, it is necessary to determine the size of the case to identify the model.