These vases and bowls are hand-painted to emphasize their individual character and uniqueness. A sugar bowl and a milk jug in a space-saving design. By putting both on top of each other, you need less space in the cupboard.
The hand-painted glaze shows that both pieces belong together. And because they are individually painted in one piece from top to bottom, the continuation of the lines also makes it absolutely clear where exactly they should be placed on top of each other.