1987, 6 July (date of issue) Czechoslovakian stamp honoring mathematicians and physicists
Postage stamp Private collection of Krzysztof Slowinski The stamp no. 2920 (Scott 2664) shows three mathematicians; the first from the left is Josef Petzval (1807 - 1891), inventor of the first portrait lens.
Catalog number: Michel 2918 - 2920, Scott 2663 - 2665
