How can you tell whether a Cartier watch is authentic or not?

Are there any specific ways to know?|||Cartier watches have a serial number on the back or inside the mechanism. Take it to a jeweler and he will tell you if it is authentic.|||If you bought it from a street vendor for $5 I'd be willing to bet it is fake.|||there are very good fakes out there...the only way to be sure is to have a jeweler open it up.