The width/height ratio of credit cards is the golden ratio
@bonifartius Yes metric paper uses the golden ratio
@valleyforge but 1/sqrt(2) is just close to golden, squareroot of 2 is ~ 1.41, golden ratio is ~ 1.61. they both have interesting properties though :)
@valleyforge isn't it ID2? that is equal to A7 which has a ratio of "1 / sqrt(2)"