Consumers with American Express Platinum cards in the U.S. have been offered the option of swapping their existing cards for one of two new designs shown here. Those designs were created by American artists Kehinde Wiley and Julie Mehretu and are called Platinum X followed by the artist’s name. Wiley is best known for painting the official presidential portrait of Barack Obama. Mehretu was recently the focus of a midcareer exhibition at the Whitney Museum of American Art in New York. Platinum cards weigh about 18 grams and are made using 65% postconsumer recycled stainless steel using ...