How do we know if an aluminum coil is new or old?

To determine if an aluminum coil is new or old, you can look for several indicators: the surface condition, such as scratches or signs of wear; the quality of the protective coating, if any, which may degrade over time; the manufacturing date or batch number, if available; and the overall appearance and shine. New coils typically have a smooth, shiny surface with no significant scratches or dents, and a consistent protective coating. Old coils may show signs of oxidation, discoloration, or other forms of degradation. Additionally, testing the coil's physical properties, such as tensile strength, can provide clues about its age, as these properties can degrade over time.