On July 1, 2021, German Post issued two stamps with the topic "Celestial Events" in wet- and self-adhesive form. All stamp forms came with matrix code. The 80 cent stamp was dedicated to the phenomenon of "Thunderstorms". The photo is from the village Hurlach, Germany, dated September 12, 2017. On July 25, 2021, the wet-adhesive version of "Thunderstorm" was withdrawn from sale. The reason was a problem with the matrix code on what must have been a small quantity of the stamps. Allegedly, matrix codes were not unique on these stamps. There were stamps with the same matrix code. This means that if two or more stamps with the same matrix code were used, then only the first matrix code registration would be valid, any further registration would then no longer work. That is, the additional “function” of the matrix code on the stamp could then not be used for stamps with the same matrix code.