Well, generally speaking, first, you should know that polycarbonate lenses are considered as the safer and thinner lenses comparing with normal ones. And Polycarbonate lenses offers you total protection from UV light and radiations too, so there are many people who choose lenses which made of polycarbonate material. Of course, it is hard to us to identify if one pair is made of polycarbonate or not. So you can just take them to the professional stores and they can give you some advices.
Yes, the polycarbonate is more durable than regular plastic lenses because of the special material. You could tell whether they are made of real polycarbonate lenses at first from the look. The plastic ones will be so easy to tell. In addition, if you could find that the real polycarbonate lenses will be so durable to use. If you have worn it for more than two years, it could be the real one.
In response to the answer above, Polycarbonate does not protect from UV rays and radiation. For example, when I used to design automotive headlamp lenses made from PC, a UV protective coating had to be added to protect the lenses from yellowing under exposure to UV rays.