Would this be considered a split die, bisecting the body? Coin is normal on the reverse. http://www.error-ref.com/median--bisecting--split-die.html
So more like this: http://www.error-ref.com/BlisteredPlating.html Thanks for looking. Learn something new every day.
Exactly. If you're ever in doubt about plating issues, you can give it a gentle poke with a toothpick, and it will usually collapse.
It's most likely a linear plating blister. However, since the ridge weakens where it crosses some of the higher portions of Lincoln's coat, it could also be a linear die dent.