331  (Early Series)   Small globe-shaped bowl with conic flaring lip.
Does this shape appear in other series?   No, not exactly although Pamela 24 and Early Series 57 are both somewhat similar.

There has been a question-mark regarding the number. This shape was initially catalogued as 33/M. Base inscriptions on several examples are ambiguous but it is now firmly believed to be 331M not 33/M. 
Every example recorded to date displays gumleaf decoration. No undecorated 331 is recorded.

Height;  8.5 - 9 cm

331 M 

33/M or 331M ?

Norman Collection
Un-numbered. Height 8.5 cm.
A PPP precursor to Early Series 331?

Trudy Viles, from trove.nla.gov.au
An advertisement by Foy's department store in the Melbourne 'Herald' dated 15 December 1938