Feel sure this is a 'triform bowl' from the Thomas Webb 'Coolie' range, and only just seen reference to this range in Hajdamach C20 British Glass - whilst looking for something else. Although my design is not shown in the book, the basic outline shape, plus the fact that mine does have the 'Webb' backstamp, must surely clinch the attribution. However, would be grateful for someone esle's confirmation to be doubly certain. My example measures something a little nearer 9.75", and not the 10" as quoted in the book. thanks for looking.