There is a Giampaulo Nason based on Murano and possibly part of the Nason family:
Worth contacting the shop to see if they can confirm - the label does look authentic, but I don't believe one has ever been seen on GMB before:
Address: Fondamenta dei Vetrai, Venezia VE, Italy
Phone:+39 041 739367
However, it could be a glass shop using the Nason name, but not necessarily selling authentic Murano glass products.