it was most probably a Zalto glass. From the first touch, each glass distinguishes from other glasses. Technical perfection is the basic principle. The glasses are not only about design. They are produced in the tradition of glassblowing of Venice, but without addition of lead oxide they are resistant against clouding. Despite its feather-light weight they maintain the best attributes of a modern glass: they may be washed in a dishwasher and are surprisingly break-proof.
I have most of them and I confirm.