Well, you know about, and then there is uh, how about the, no not that either. Gee, you may be right.
If it's raised it's a die crack. If not raised it's a plating issue. I'm leaning to the plating issue as I don't see it raised.
I agree with @Collecting Nut Looks more like a fissure to me. Also considering the difference of colour surrounding the line in the coin I would go towards lamination error.