Traditionally, each wedding anniversary is celebrated by giving a gift made from a different material. The practice originated in medieval Germany, where it was customary for friends to present a wife with a wreath of silver when she had lived with her husband 25 years. The silver symbolized the harmony that made so many years of matrimony possible. On the 50th anniversary of a wedding, the wife was presented with a wreath of gold. Hence arose the traditions of "Silver Anniversary" and "Golden Anniversary".
This medieval practice has since been elaborated upon in modern times. For instance, diamonds are traditional anniversary gifts in the 10th, 60th and 75th years. Year 60 was probably added when Queen Victoria celebrated her Diamond Jubilee after ruling 60 years on the British throne.
Anniversary Years & Gifts