The German parliament has agreed to return a painting that's been hanging in lawmakers' offices for decades after learning that Nazis had looted the work from its Jewish owner.

A portrait of Germany's first chancellor, Otto von Bismarck, the work was painted in 1896 by the then-fashionable artist Franz von Lenbach and owned by Herbert Gutmann, the son of Dresdner Bank's co-founder, from whom it was taken in 1934, when Nazis "aryanized" the bank. No value has been released for the painting, but portraits by the artist that are scheduled to be auctioned at the Berlin-based auction house Grisebach this month, including two of Bismarck, are estimated between $4,400 and $44,000.

Gutmann's heirs tracked down the work to the parliament offices in 2007, and parliament experts established the legitimacy of the claim. The work had been purchased from a private collector in the 1960s. “Clearly this picture belongs to the heirs and we’ll return it once an agreement has been signed with them,” said parliament spokesman Christian Hoose. “We want to give it back as soon as possible.”

The discovery calls into question how many other looted works could be in the parliament's collection, particularly among the 200 pre-war works installed at the Bundestag, or lower house. Of the 4,000 artworks on loan to lawmakers and others in the Bundestag, said Hoose, 95 percent are post-war, due to the government's effort to "look ahead." Among them are examples from Neo Rauch, Gerhard Richter, and Georg Baselitz.