To check a Rolex is authentic, there are a few steps you can take: 1. Check the serial number against the Rolex warranty card. If necessary you can bring the watch to service centre and check it against Rolex's database. This will tell you whether the Rolex is genuine and when it was made. 2. Inspect the case and dial. Authentic Rolex watches have a high level of precision and attention to detail. Check the case, dial, and other components for any signs of poor quality or poor workmanship. Look for details like symmetry, alignment, and finishing. 3. Look for the Rolex crown: The Rolex crown is a symbol of authenticity and quality. It should be present on the watch's face, crown, and clasp. 4. Verify the movement through hand winding. A real watch movement should be precise, smooth, and consistent. You can feel it when winding. Also look at the indicator and date aperture to see if they move smoothly or not. 5. Seek professional help. If you're still unsure whether the Rolex is authentic, take it to a reputable watch dealer. They may be able to provide a more thorough inspection or have advanced tools to check the watch's authenticity.