How do you spot a fake in Dior sunglasses?

I have the Airspeed sunglasses but how do I know they are really authentic?|||On Dior sunglasses, it should say Christian Dior on one of the sides in little white writing. On the other side, it should say Made in Italy followed by the Model and then the color codes of the frames and lenses. You can easily verify the model numbers at like Amazon.com. Find the color you have on there and scroll down to find the Model number/color code. Hope that made sense!