Stamp Stories from around the world

I found this interesting imperforate stamp in an old stock book with only common German stamps. There was also a similar 5 F imperforate stamp. The stamps are issued in connection with the “Exhibition of Flight and Navigation” in Marseilles in 1927. In the Michel catalog I could only find them as perforated with a CV of 650 €/$ in mint condition (**). I brought them to an auction house who stated, that they were genuine. They found out, that the stamps probably originated from an imperforated minisheet, that was issued in connection with the exhibition. The stamps were sold for 3.400 Dkr. or around 500 $.