Closed settings are used when it is desirable to have metal under the stone so that no part of the stone below the girdle is visible. Early rings were set this way and sometimes foil or paint was put on the back of the stone before setting to change its color or appearance.

Georgian Citrine Pin with Closed-Back Setting - Front. Photo Courtesy of Lang Antiques

Georgian Citrine Pin with Closed-Back Setting - Reverse. Photo Courtesy of Lang Antiques