My late 2011 MBP 13" is like that. I also noticed when I swapped the RAM modules that the back plate is thinner and bends way easier compared to my former early 2011 MBP 13". Like "dong-dong" instead of "tap-tap" when hitting it with a knuckle.
my screen broke and they replaced it on such as on the photo
but i don't like it because it left fingerprints and i just don't like this way of aluminium
and in the end it looks like HP or Asus .... old stylelikes me more
My early 2011 model is like that. I always assumed it was because I cleaned it a lot with a cloth, its only noticable under a bright light or at a certain angle![]()
Looks like a skin probably.