A posset pot of English Delftware, which is tin-glazed
earthenware, made around 1660
These pots were common wedding gifts and became family heirlooms. This particular pot is the size of a large teapot and the blue and white decoration imitates Chinese porcelain and shows the popularity of Eastern design at the time.
UPDATE in response to comments from here . Also I took the wording directly from the card with the object:
English delftware is tin-glazed pottery made in the British Isles between about 1550 and the late 1700s. The main centres of production were London, Bristol and Liverpool with smaller centres at Wincanton, Glasgow and Dublin.