Glass crystal model

Dr. F. Krantz, Bonn am Rhein
Glass models of a hexagonal and tetragonal crystal from a series. The height of the hexagonal prism is 14.8 cm, the height of the tetragonal bipyramid is 20.2 cm.
Internal silk threads materialize the crystallographic axes; red for the c-axis, yellow for the other axes.
On the tetragonal crystal model a small glued label indicates: "16 | Dr. F. Krantz | Bonn a. Rh." On the hexagonal crystal there is a similar label indicating: "10 | Dr. F. Krantz | Bonn a. Rh.", and another gilded label with the Krantz logo and the text "Dr. F. Krantz | Bonn am Rhein".
Both models, first half 20th century.

private collection