6 September 1983, German Democratic Republic
Death Bicentenary of Leonhard Euler
design: A. Bengs
The out-line geometry is Icosahedron and the formula is thought by Euler on the right. The formula is “v (vertices) – e (edges) + f (faces) = 2” in English. Some people think this is very beautiful formula – well, for me as non-mathematician, polyhedra as three-dimensional objects are more attractive.