Antique Kays Excelsior 40 pound curling stone in its original leather case. Kays of Scotland is the only remaining UK manufacturer and supplier of curling stones. Founded in 1851, Kays retains exclusive rights to harvest granite from Ailsa Craig, a privilege granted by the Marquess of Ailsa. Kays of Scotland produces the only stones used in competition by the World Curling Federation and is the sole supplier of curling stones to the Winter Olympic Games.