Obverse is a 67 all day long. Reverse has some light mellowing which might or might not have been there at grading time. Going with 67, but 66 would not surprise me.
I am not exactly sure I would call it a discoloration (I don't know what else to call it either), but it is the coin.
My picture emphasizes the marks on Abe's bust. This coin has a great strike, great luster, and the only marks I see are a few small left over planchet marks. As Thad mentioned, the is a streak on the reverse. I am not sure just what to call it. It might be the early stages of wood graining. All I can say is that they were awfully persnickety when they only gave this a 66 unless they are really that averse to woodies.
Everyhone moved all over this week. However, Leadfoot is still leading. Top 10. Columns are rank, name, average, and number of guesses. Leadfoot 0.325 42 ldhair 0.333 26 Animosity 0.360 27 rzage 0.375 34 Duke Kavanaugh 0.410 41 Shoewrecky 0.414 31 mark_h 0.447 49 bahabully 0.487 41 BadThad 0.538 41 jcakcoin 0.553 49
It's early stage verdigris, I've seen it before and removed it from red coins. It is very easily removed without effecting the coin in any way.