looking at this coin it has a light green and purple tone for only 25 cents. yup, i'll grab that. however, what appeared to just be damage in back of abes head is something else too. is it a die clash? what is going on with the extended tail on the 9? die gouge above L in pluribus? light green tone can be seen on obv around liberty and purple on the rev top left quarter of coin. a little hard to photo.
I think it's just a plating issue above the letter L.. These are Zinc plated Steel Cents. The rest of the issues in question could be Die Deterioration. IMHO The 9 is interesting though
It's been plated, and therefore everything you mention in your first post is the result of the plating. color, toning, extension on digit, etc.
