I often buy my sunglasses second hand from eBay as I am not rich enough to afford new sunglasses Is there certain signs to look out for across all Oakley sunglasses which will give confirmation if they are genuine or not? Like for example with Prada sunglasses i know that on inside of arm there should be a model number in format of "SPS 12A" or "SPR 12B" etc also there should be frame sizes written in special format, and on newer models upto 10 years old there is always a serial number etched onto the lense. So what kind of things can I look for when identifying the Oakleys for authenticity? Any help would be appreciated. p.s. I asked a friend at my office and he said about some test where you pour water on the lense and on real oakleys the water acts differently then when you poor it on fakes. Something about it running off the lense and not bunching into small droplets.