Exposure to the elements. Looks like the plating/substrate are separating and creating a visual anomaly.
DDD- Die Deterioration Doubling You can see the Striations on the field. Worn Die issue.. No need for 2 separate threads.
Sorry, the other thread is a different coin I just came across. 1963 D that I'm pretty sure IS a DDO. Would you mind taking a look at it?