Between 1973 and 1989 the East German police, known as the Stasi, seized more than 200,000 objects in hundreds of raids, according to experts and official archives. As part of a broader government program to secure Western currency through the sale of the art, the police went after collectors like [Helmut] Meissner, who, when he objected, was sent, at 79, to a psychiatric hospital and portrayed as an enemy of the state.

But now, Mr. Meissner’s story has resurfaced, as his son tries to reclaim what he says was one of the most valuable items seized from his father more than three decades ago: a 1705 still life of four chestnuts by the Dutch artist Adriaen Coorte. In court filings in Munich, the New York family that now has the painting says that it was bought 25 years ago, legally, in good faith and with no understanding that it had been seized by the Stasi.

Until recently, few Germans realized that the covert program, with its echoes of Holocaust-era looting, had ever taken place in the German Democratic Republic, said Gilbert Lupfer, the lead researcher for Dresden’s state art collection.