Strange patches on Side Window Panel

[WingZero30]

Hi guys

I have storm trooper case and for few weeks I have noticed that for unknown reasons the following patches/markings have appeared on the window. On the inner side the surface has same texture/smoothness as rest of the window. However on the outside the surface feels 'dry/rough' where the patches are. I can't think of a single reason how these appeared and would love to get rid of these .

Any suggestion ??

Spoiler

Spoiler

 

[WingZero30]

Thanks guys for your help. It doesn't scrape off unfortunately. Just gonna have to contact Cooler Master now.