This aluminium ball is traditionally known in Portugal as "bone sphere" and used to cook rice in a flavour some broth (where meat and vegetables are usually cooked as well), to make sure the grains stay together. It can be used for other culinary (making tea for an army, for instance) or decorational purposes (hang it with a candle inside for a nice glow to a room).
This unique Portuguese creation originated in the North of the country. It comes with a lock and key and is available in two different sizes.