In 1851, The Baden 9 Kreuzer Error was a postage stamp error produced by the historical German state of Baden. On May 1st 1851, Baden’s first postage stamps were issued.
The “9 Kreuzer Green” stamp was a color misprint of the 9 Kreuzer denomination that was printed in green instead of pink. The green color was intended for the 6 Kreuzer value, but apparently the paper sheets were mismatched. Only three cancelled copies and one unused copy of this error are known.
The usual explanation for the occurrence of this error is that the printing plate was used invertedly. However, this theory cannot be correct because the stamp was produced in a single printing. It must be assumed that the printer had unintentionally used the wrong plate for the green paper: instead of a “9” he had read a “6”.
The error is one of the greatest philatelic rarities in the world. The 9 Kreuzer error was not discovered until 44 years after the stamp was issued.
The only unused copy appeared in 1919 for the first time. And In 1991 it was first auctioned by David Feldman and in 1997 it was auctioned again and was sold for 603,750 US$. On April 3, 2008 it is going to be auctioned again by David Feldman. A sales price of 1 to 1.5 million euro is expected.
By December 31, 1871 the whole postal system of Baden was handed over to the German Reichspost. Since then the postal history of Baden is the one of the German Reich. Baden’s stamps could only be used until that day, but an exchange to valid stamps of the German Reich was possible until February 25, 1872.