Technique looks like pulegoso, though in the 1930's Carlo Scarpa did some work with a variation he called Sommerso bubble. A number of other factories apart from Venini also worked in pulegoso including Seguso, what size are they as a little difficult to tell from the pictures. I must say my first though is that they look more 50's than 30's, but maybe Laura will pick this up later and help out.
Paul