How do I identify a good quality aluminum coil?

To identify a good quality aluminum coil, consider the following factors: purity indicated by the alloy number, surface finish which should be smooth and free from defects, thickness consistency, and mechanical properties such as tensile strength and elongation. Check for certifications or quality standards compliance. Look for uniform color and absence of oil stains or rust. The coil should have precise dimensions and be free from dents or scratches. Additionally, consider the supplier's reputation and customer reviews.