421  (Early Series)   Small teardrop-shaped jug.
Does this shape appear in other series?   No - (none recorded in image database).
There is another Early Series jug of similar teardrop shape but it has a different handle and is larger; Early Series 64.  421 is a dainty little thing.

Height; 9 - 9.5 cm

Norman Collection
421 (right) with Early Series 64