Baden 9 Kreuzer Error most valuable German stamps

Baden 9 Kreuzer Error is the most rare and valuable German stamp with only 4 in existence. The error that makes this stamp so valuable consists in the following: it was supposed to be printed in pink but a few sheets were printed in green. As the Postal Service explained, it planned to issue 6 Kreuzer stamp in green that is why such an error occurred. This adds to the history and rarity of these stamps. Nowadays Baden 9 Kreuzer is worth around $1,545,000.