You like dragons?
The display on the 520 and the 525 are just normal IPS LCD displays covered with scratch-resistant glass. At least something is being done with regard to the display.
One thing I do know, though, is that plastic scratches easily. :3
I find it interesting that of all the devices I currently use, I can sort it out like this, with regard to the screen cover:
Plastic for my laptop, feature phone, and the 3DS XL's bottom screen.
Glass for my tablet, smartphone, and, apparently, the 3DS XL's top screen. (I think it's just reinforced with glass fibres...)
Guess which displays get a lot of scratches