In the process of anodizing, the product can lead to some minor dichromatic outcomes or some smearing at the surface level and also you'll see some hook marks within the case (shown in the 3rd pic.) If there's a mark or imprints located in places where it's not visible after assembly, it is not eligible for R&R.
A-Stock: Below 1mm imprint, Scratches below 3mm
B-Stock: Over 1mm imprint, Scratches over 3mm