i am always interested to see the reverse of coins posted. Will leave others to opine about the mint marks.
Sorry, but it's damage. The copper plating split and the zinc underneath is corroding. It's similar to a car fender rusting after the paint is scratched. It's not uncommon to have split plating on cents from the 80s
Yet another crappy Zincoln with issues. I sure wish they would retire the cent if they can't produce something better.