Seems to be a prototype / experimental bowl from Vistosi's factory archives (I got it a while back from D&A). I'm assuming prototype because the design is a bit rough around the edges.
The body of the bowl is formed entirely from a single piece of glass that's been 'folded' in several places. At the base it is compressed flat to make the bladed foot, at the top rim it is folded to encase a ribbon of opal glass, and near to the outer rim it is folded over once again to encase a ribbon of dark blue glass. The edge of the bowl is lined with a lighter blue ribbon (not encased).
The bowl probably dates mid/late 1980s. If anyone knows the designer, or if it was ever tidied up and put into production, I'd love to hear!