The paintings are the second spectacular Dix find from an estate left by the daughter of Martha and Hans Koch, Düsseldorf art collectors at the time, whose lives became entangled with Dix's.
Last year a valuable preparatory sketch for the major lost work “Winter Fairytale” was discovered in a dossier that had been left unopened for decades.
The works include watercolours “Night-time” and “Soubrette,” and a preparatory work for Dix's famous portrait of the art deal Alfred Flechtheim. A large-scale watercolour “Strich III,“ showing a street scene with prostitutes, was also found. Gallery owner Herbert Remmert said some of the works were worth more than €200,000.
Remmert said the Koch estate could contain more discoveries – it is also said to contain children's books painted by Dix.
Remmert's gallery tracked down the lost works to Koch's granddaughter in Bavaria. Martha Koch fell in love with Dix when he moved to Düsseldorf in the 1920s, and Hans Koch divorced his wife as a result of the relationship.
Dix is famous for painting the uglier sides of sides of society, and particularly for his nightmarish impressions of the First World War. His creative highpoint is considered to be his paintings of Berlin from the mid-1920s.
Remmert is planning to show the newly discovered paintings along with other works in an exhibition in Düsseldorf to mark Dix's 120th birthday later this year.