the W56 shown in Leslie Jackson (I don't pretend to understand, but Jackson offers several alternative pattern Nos. against this one shape, in her book), agrees with the shape of Della's link to W56 .............. but I'd suggest that neither of those really agree with the shape of bat's vase.
The difference appears to be in the curvature of the outline - quite pronounced in Jackson and Della's link - more so than this piece, and the optic ribbing - which should be pronounced - looks absent? Does this vase have strong optic moulding? W56 is from the Wealdstone range ..... c. 1930 - 35.
But this one does look to be sapphire .............. I always remember getting taken to task some years back by Emmi Smith for forgetting the word has two 'pees'. We've not heard from Emmi for a long time - I hope she's is fit and well still.