Does this shape appear in other series?  Yes -  'A' Series / Kerryl A125 according to a shape-book entry but no example of that is recorded.

Height; 9 - 9.5 cm.

This is one of a small group of 500 numbers that are not part of the 500 Series but instead are associated with the Later Series. In a Later Series shape book numbers 500-506 are interposed between 165 and 166. The reason for this group of anomalous numbers is unknown. Some examples have twig-handles (a feature common in the Early Series but otherwise rare in the Later Series) and carry the number suffix 'H'.