1/4 I was surprised how close I came on the last 3. Just a few points off on the AUs and slightly over shot on the red cent. Fun stuff!! Thanks for sharing these and making a learning experience out of it.
I was trying to be realistic and bringing into play nasty things like scratches and appearances that might be objectionable to a buyer. Specifically: 1930D Obv: Field and image have many specks that look like little holes. Rev: Lacks the markings of the Obv, but field is multicolored and there are scratches above and left of "U", a prominent scratch between "N" & "T", and scratches below AMERICA. 1931 Obv: Image is sharp but both it and the field have many scratches. Field shows vertical and horizontal scratches behind head and squiguilly lines in front of the face. There are markings on Abe's forehead, upper cheek and nose. Rev: There are blatant scratches above and to the left of "O" and between "N" & "T", and markings below AMERICA. 1931S Obv: Excessive wear as evidenced by there being no mark between bow tie and lapel---that alone would disqualify an VF rating---and scratches in Abe's face. Rev: Excellent but preempted by Obv. I do not see how these shortcomings could be ignored in a grading.
First off, you are looking at the coin something in the vicinity of 12X. Graders grade with no magnification or at most 5X. 30-D Scratches do not make a coin circulated. They just lower the uncirculated grade. 31 Wear is the PRIMARY determinant of grade. Minor scratches may lower the grade a level or 2, but nothing more. 31-S This date is not noted for strong strikes. Hence the weak tie. That minor imperfection has no affect on circulated grades. FWIW, a F15 Lincoln has worn so there are only "slight hair and coat details" and "most of the wheat lines are visible".
Regarding chatter, AU coins are still graded considering marks in the higher grades. A coin that wouldn't grade 63 or higher if uncirculated would not grade AU58. A slightly worn MS60 would grade no better than AU53.