For thousands of years, rings have been worn as finger jewelry by civilizations across the world. Although today rings are primarily worn as a form of adornment, rings can also serve both symbolic and practical purposes. Rings have been considered a symbol of love for centuries, with couples gifting one another promise, engagement, eternity and wedding rings. Since at least the 16th century, diamond rings have been used as a mark of engagement. Popular diamond ring jewelers today include De Beers, Cartier, Harry Winston and Tiffany & Co. Signet rings have been produced since antiquity, used to stamp wax with a seal as well as to present a personal or family crest. Birthstone rings are also worn to mark an individual's month of birth or star sign, varying from emerald to ruby. In the UK, sovereign rings bearing either a real or replica golden sovereign coin are often considered a sign of patriotism.