I believe the size and shape of the "refrigerator dishes" used as promotional giveaways like this were sized to fit on the shelves, or some in the door shelves of the refrigerators they were selling. Looks like this cute pitcher would slip right onto the shelves of a vintage refrigerator. Even with a few dings and flea-bites, it's a wonder that these gems have survived all these years. To find a piece in the thrift store is a victory in itself - antique dealers usually price these things pretty high.
I have a (small) collection of Hall China pieces that were made for Hotpoint, Westinghouse and Montgomery Ward promotions. While they don't stack or nest together, a couple of the water or milk pitchers were obviously sized to fit into door shelves or make the most efficient use of space. I'll have to take a couple pictures of the Hall (and Harker) I have, it really is pretty stuff.