This odd looking marbled green genuine carved onyx crock is a French butter bell or butter keeper. You simply pack a softened stick of butter into the cupped lid piece, add water to the larger container, and invert the butter filled lid into the base. The water creates an air tight seal around the butter, keeping it soft and fresh. The 2-piece crock is 4" diameter by 4-1/2 inches high and is in excellent condition with no damage.