Ardy:
This looks quite sophisticated to me. The spirals are well done, the bottom is nicely and neatly finished, and, the clincher for me, it does look like the top red has been applied separately. That process is called incalmo and is not an easy one, from what I've read. I can't suggest any possible makers; it could be Murano, though it looks later, and I think that there are few current studio glass makers who could make it, which again would make it later. On thinking it through, though, I can't imagine why a studio glass maker wouldn't sign it. TxSilver has a great eye for Murano, I wonder what she thinks.
David