Tell us what you suspect and that would help. Are you talking about the mark on Lincoln's jaw, the width of the rim, etc.? (Also a nitpick, but cropping your picture would make it look nicer... good quality picture, though!)
The only thing I see is A Misaligned Die Strike. See how it's thicker on one side and thinner on the other. Minor error. The marks on Lincoln's face is just damage.
Books? Who needs books? You just ask a question on the Internet. Staying "online only", and avoiding books, is the best way NOT to approach this subject.