I am not sure what you mean by dd, doubled die? d over d? I think though that it is zinc rot, this is very common on 1980's cents where the plating would split exposing the zinc core causing it to deteriorate. Some close up pictures of the area should help show it, if you can't then check the area very closely with a magnifying glass to check for a break in the copper plating.
We've already told you what it is. The mint mark area in those days was prone to having cracks in the plating. Moisture gets in to the zinc core and begins to corrode. That's what you have. No rpm or anything else. This is a common occurrence and the coin has no added value.
HH
enamel7