Boiling water would allow it to expand, but the drop of water that leaked is almost indistinguishable. This only happened with boiling water, but it did not leak with very hot tap water. See the last picture which is enlarged. The teapot is for decorative purposes. The teapot is shown in the photo in my grandmother's curio cabinet in the 1950s.
Its size is 5.5 inches tall including the lid, and it has a diameter of 4.5 inches not including the spout.