30(Early Series) Jardiniere with flared lip, ribbed at base.
Does this shape appear in other series? Yes - Later Series 500 is like 30 s. A 21 cm version is also recorded as Shape 'C' in the Alphabet Series, with applied decoration of birds. Another jardiniere rather similar, but even larger, is Early Series 241.
The shape book shows two sizes, suffixed 's' and 'L'