All my Oakley's have made in U.S.A stamped/embossed into the inside of the frames arm,so genuine ones won't have made in any other country except the USA,and if you run your thumb along the lettering you will be able to feel the letters,metal frames will have it painted on though.Was something about the Oakley O letter on the frame arms.It should be a raised letter of the O,like on my whisker ones the O is separately stuck/glued on its never printed or painted onto the frames.
Probably do a search on the net to find out more.