Just for information, thinners (30% acetone, etc) and acetone free nail polish remover (ethyl acetate and isopropyl alcohol) won't touch it.
In fact careful examination reveals that a tiny section to one side of the lens is not damaged. The bad news is the "islands" that look like a coating on top of the coating are infact the remains of the original optical coating
. It is well and truly etched!
Nasty stuff!
Al.