This 1999 penny seems to have a "vein" on the top of Abraham's head, just below his hair? Am I just over thinking it, or is this a minor error? (It's easier to see in person.) I'm probably just over thinking. Lol. (Sorry, bad pics.)
A die crack or die scratch on the forehead is a pretty common location on older copper wheat cents. On newer copper plated zinc cents you can also get plating blisters that look a little similar.
That's the cranial-temporal vein. There's one of these on each side of the cranial-frontal lobe. Or it sounds it could be, don't it?