Gottlieb Incredible Hulk.
So I assume this is planking or ribbing?
Seems a bit weird because it's not just lines but it's got "swirls" or "whirlpool" marks also.
Anyhow. It won't clean off, it won't buff off, it won't wet sand out.
Has anyone tried heating up the playfield and trying to "melt" the paint slightly to re-fill or re-flow the paint?