Removing Keyboard Protector Imprint from Screen

I have an A1466 model (But I guess this can be relevant to any laptop in general),that has has a keyboard protector imprint or stain remaining on the display, the previous owner has obviously never taken off the KB cover when closing the display. I have tried rubbing it with screen cleaner & ISP but it is still there, Is there any reliable method to remove this that anyone has tried with some success? My guess is that it has left a permanent marking on the anti-glare coatings :( A reason why I never personally used them.