Absolutely gorgeous, I am drooling (how attractive haha!). Where did you get this from Charles? I too have seen a few pieces like this on eBay and they are almost invariably marked Italian.
Perhaps the corroso technique? Or perhaps the other technique used by Paolo Venini, the name of which escapes me at the moment... I know it is in Nigel Benson's small green Miller's guide, it's a pinkish diffused looking vase... aaaah can't think at the moment!