If there were shown the whole set then all would state: creamer!
Object is galvanic gilded inside too. Normally inside gilded objects - e.g. hollowware and spoon or forks and other server — were gilded for sensible contents; e.g. cream, milk, wine, stewed fruit, salad …
As Pat said, it is a sugar scuttle, made in several different forms to resemble the much larger coal scuttles of brass, copper, etc., most originally came with a matching scoop.