A 75th anniversary is called the diamond anniversary. It is sometimes referred to as the diamond jubilee and is considered the pinnacle of anniversary celebrations. Diamonds are the strongest substances on Earth, as well as one of the most desired, and therefore represent such an esteemed celebration.
Anniversaries have long been marked by a traditional gift that is specific to each year celebrated. These celebrations get their root from Medieval times when a husband crowned his wife with a silver wreath for 25 years of marriage and a gold wreath at 50 years. Even today people refer to the 25th anniversary as silver and the 50th as gold.