Question

why did the us flange change their appearance

Answer 1

The U.S. currency redesign, which includes changes to the appearance of flanges—if you're referring to currency notes—was aimed at enhancing security features, improving durability, and modernizing the look of the bills. The U.S. Department of the Treasury and the Bureau of Engraving and Printing periodically update currency to incorporate advanced security features that help prevent counterfeiting. These changes can include new colors, different textures, and updated imagery that reflects historical figures and aspects of American culture.

If you were referring to a different kind of "flange" or a specific type of change or context, please provide more details, and I'll be happy to elaborate!