Patek Philippe is one of the most expensive brands.FABRICE COFFRINI/AFP via Getty ImagesA premium watch authenticator said there are telltale signs of fake watches.He said with counterfeiters getting more skilled, it is often difficult to tell the real from the fakes.From the paint on the hands to the magnification of the date window, here's how to check.This as-told-to essay is based on a conversation with Ng Yong Shen, a vice president with Re-Loved Luxury, a Dubai-based secondhand luxury retailer.