How long you have been using it and in what conditions? and is that black case worn-off or brown case getting darker along the edges?
Looks like it underwent some heavy rubbing..
How many months of use is that.
I bought it the day the iPad Air came out in the uk.. Can't remember the date sorry.
It's the brown one getting darker. I haven't altered it in any way to make it look like that but it does get put in and out of pockets/bags a lot.
Oh I've never cleaned it either.