Some of it might be environmental, but probably most of it is improperly mixed alloy. See http://www.cointalk.com/t65353/.
I like this coin also, but you don't agree. Fewer nicks than the 15-D and the obverse has better luster and I see no evidence of wear in hand. I know I am prejudiced, but I think the spots keep it from a 65. PCGS agrees with you at 63.
Duke continues to widen his lead, but his is going to start dropping off his good scores soon. Top 10. Columns are rank, name, average, and number of guesses. Duke Kavanaugh 0.341 46 bahabully 0.458 50 Leadfoot 0.543 48 Coinguy56 0.545 35 swhuck 0.564 41 ddoomm1 0.583 38 Shoewrecky 0.643 30 BadThad 0.646 50 mark_h 0.646 50 jallengomez 0.711 40