300  (Early Series)    Big barrel-shaped vases with high flaring conic collar.

Does this shape appear in other series?    Yes - 500 Series 523 and Later Series 23 are like 300L.

Two sizes are recorded, with size suffixes s and L.

300 LM

An example with grapevine decoration is also reported. No photo.
GDL Auctions
Hurnall's Antiques & Decorative Arts
Collection; Lyn Wallace
300 L
       Height; 20 - 24 cm

Collection; Brian Tonkin
300 s
       Height; 17 cm.
Collection; 'W"
    Collection; "W"
Comparison; 300-L and 300-s