12 January 1968, Germany
“Technology and Science”
1000 years of ore mining in Harz Mountains
design: K. O. Blase
Cubocutahedron ( top left ) is one of the Archimedean solids, and the lower right one is an almost Truncated tetrahedron ( well, in progress to be ). The other two polyhedra are progressions and they must be the crystal shape of chemical formulas of lead(II) sulfide and Zinc sulfide. Nature is full of wonders!
Using four colours, this stamp is really delicately designed and nicely printed. I love this crispness.