yes, it is glass. best guess by most people is that it is bohemian with decoration by as yet unidentified decorator. some have proposed that the decorator bought blank glass from the Harrach company.
By the way, ty for all your help. Your use of the term "mystery mark" gave me some new ideas for searching the internet. Could it be Karl Pohl/Pfohl? He was a Bohemian decorator/engraver.
