Superimposed Fraunhofer
The Superimposed Fraunhofer is (also known as a Super Fraunhofer, Fraunhofer Overlay, etc.) is a German postage stamp issued on February 12, 1987 in which the image of Joseph von Fraunhofer demonstrating the spectroscope is superimposed on the color spectrum bar.
At least three superimposed sheets were found during the production process and destroyed. It is believed that only one misprinted sheet of 100 stamps got through unnoticed.
The job of designing and printing the stamp was carried out in a great rush; engraving began only on January 31, and stamp printing on February 11, in sheets of 100 (contrary to the usual practice of printing 400 at a time and cutting into 100-stamp panes). Since the stamp was printed in a spectrum of colors, each sheet had to be placed into the flat-bed printing press using Gnomon algorithm techniques, an error-prone process that had resulted in superimposition errors in stamps of 1983 and 1985.
It is probably the most famous error in German philately.