with panzaldi and I see PVC damage as well as residue still on the coin. Acetone to remove it now before it worsens IMO. You can make it out on the reverse along the rim at 7:00 & 11:00 as well as the inner folds of the upper corn sheaths, plus all around the rim on the obverse. That's the green stuff.
I like the crack though, makes the coin more interesting to me. I wonder how long the obverse die lasted and if it ever became a full cud obliterating the date? That would be something to see.
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013! ANA Life Member #3288 in good standing since 1982, EAC Member #6202, NBS Member, 2¢ variety collector.