These piece are not Seguso. There were a few in a Quittenbaum auction recently with the label of a different firm. I'll try digging the catalogue out later and posting the maker.
chuggy, where did you get the Seguso attribution? While they did a lot of corroso pieces, so did other companies, such as Alfredo Barbini. If your source is Pina's books, take it with a big dose of salt (or sugar, or whatever). She takes her attributions from the owners of pieces without any double checking.