Rolex watches are probably one of the most copied watches in the world. The best thing to do is to take your watch to a qualified watchmaker and let them determine if your watch is genuine Rolex or not but here are a few tips on how to spot a fake Rolex.

Many of the counterfeits use very good mechanical movements that lets the sweep second hand glide around the dial chapters, a Rolex trait. The fakes use a common quartz movement where the sweep second hand ticks every second as it steps around the dial. But be careful, Rolex made a few models that used quartz movements.

You can remove the watch band. Check between the lugs at the 12 position and see if it has an engraved "Registered Design" number. If you see no number, it is fake.

Check between the lugs at the 6 position. Here you should see a serial number of the case. If there is no number, it is fake.

If there is a glass crystal on the back of the case, so you can see the movement, your watch is fake. 

If you see a "Rolex" that has the Rolex name engraved on the case back.  These are also fakes.

On gold colored watches, look for signs of wear on the lug ends and on the case backs. Fake Rolex watches will often display area where the gold color has worn off, exposing the white colored base metal of the case below.

Check the watch bands and look at the clasp. A genuine Rolex clasp is nicely engraved with the old original Rolex emblem. This appears on both gold and stainless clasps on watch bands.

Another thing to look for is the weight of the watch. Gold Rolex watches are very heavy as compared to the fakes which are very light for their apparent mass. This is because the specific gravity of gold (Au) is much greater than the specific gravity of a base metal. Stainless steel Rolex watches also have more weight to them because stainless is also much heavier than the base metal used in bogus watches.