As far as I can find out Hermann Wintersteller was active at Vrigstad Kristall Glashytta which opened in 1982 and closed in 1987.
He lives in the village of Orrefors and is approx. 76 years old.
In November 2012 there was an auction of many of his pieces ( signed Orrefors Glasateljé HW ) on lauritz.com. I wish I had bought some of them, they were stunning but I was busy and forgot about the auctions