This 1976 Werner Herzog film is centered in a small village (and as such, some dialect and heavier accents are used), where the secret of the ruby glass dies with the maker.
While many of the cast may be relatively unknown today, actor Clemens Scheitz has an interesting filmography. He was in the 1979 version of Nosferatu and also plays in Stoszek and Jeden für sich und Gott gegen alle (The Enigma of Kaspar Hauser).
We see the difference between the every day person and the aristocracy, which may make an interesting comparison. I would recommend showing clips rather than the full film for such a discussion, as the pacing of this film is quite slow. That, combined with the heavy accents, may make this film difficult to use in an educational setting. There is also some (non-sexual) nudity about 20 minutes into the film.