My late 2013 13" rMBP has a very very unnoticeable imperfection, It causes no problem by itself but it may cause the glass on the display to brake when something pushes the left corners. The left hinge is about 0.5 mm above the place that it should be so if you look at the left side while a light source is at the back( and lid is closed) you will see the plastic around screen doesn't touch the surface on the left side and it's about .5 mm above the surface, but in the right the plastic touches the surface, I don't whether this is fault of assembly and serviceable or it's a defect in the sizes of the parts of the rMBP. I am sure most of you don't know about it because it's very very unnoticeable, you should put your MacBook between a light source and your eyes to see this gap.
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