Cardboard crystal model
Dr. F. Krantz, Bonn a. Rh.", first half 20th century
Cardboard model (25 x 10 cm) of a tourmaline crystal from a series of 60. These models were offered varnished to prevent damage.
A small glued label indicates: "25 | Dr. F. Krantz | Bonn a. Rh.", first half 20th century.
Below are pages 162-164 from Krantz catalog 18, 3rd ed., describing their cardboard models