Hi Peter,
I think in part the lack of info regarding Stölzle, may be due to the company being heavily involved in packaging/container and pharmaceutical/medical glass. The pressed glass from Hermannshütte, seems to have been secondary to these two main types of glass.
As to their factories, they had at least 8 or 9 plants in Austria, Hungary and Bohemia, and certainly one of the Bohemian factories, built just after the turn of the 20th century at Chlum u Trebon, stood idle for long periods, before being leased to Vaclav Hrdina, of Stepan Hrdina a Syny in the early 1920s.
Regards,
Marcus