 The collar is an accessory worn around the neck , over the mantle and secured with white ribbons tied in bows on the shoulders . Like the mantle , it was introduced in the 15th and 16th centuries . Made of pure gold , it weighs 30 troy ounces ( 0 @.@ 933 kg ) . The collar is composed of gold knots alternating with enamelled medallions showing a rose encircled by the Garter . During King Henry VII 's reign , each garter surrounded two roses — one red and one white — but he changed the design such that each garter encircled the Tudor rose . 
