Nr. 931
Klein bottle
Row: 1

Nr. 373
Boy's surface with symmetry axis
Row: 1

Nr. 297
Boy's surface with symmetry axis
Row: 1

Nr. 301
Heptahedron (one-sided surface)
Row: 2

Nr. 400
Desargues' thesis in space and in the plane
Row: 2

Nr. 338
2 stereoscopes
Row: 3

Nr. 338
2 stereoscopes
Row: 3

Nr. 359
Two regular each other penetrating tetrahedrons
Row: 4