Does this shape appear in other series?  No - (none recorded). Curiously however, it does look identical to another Early Series shape; Early Series 23.   The distinguishing feature compared  with 23 is the twig-handle. None of the many recorded 23 examples has a twig-handle whereas every one of the 221 pieces does. It would be most unusual though for the presence of a twig-handle to warrant a separate shape number - normally it does not even warrant a suffix. Other pieces in the 220 number range, however, do include similar anomalies; perhaps something strange was happening just then.  A likely explanation here is that the similar-shaped 23 had already been discontinued and its number re-allocated to another shape, prior to 221 being introduced.

Height; 10 cm