SARASOTA, Florida - Collecting poster art was a passion for Hans Sachs, a well-to-do German dentist who adorned his Berlin home with the bright-hued work as World War II began to simmer around him.

Sachs meticulously cataloged his collection of 12,500 posters and was credited with elevating commercial graphics to an internationally recognized art form during the first decades of the last century.

Then came Kristallnacht, the "night of broken glass," and - like many German Jews - Sachs lost nearly everything to rampaging mobs of Nazis. It was Nov. 9, 1938. The Gestapo arrested him and hauled away his collection, which he never saw again.

Today, several thousand of his posters - likely worth millions - are stored in a German history museum, and Sachs' son wants them back. The museum is refusing to hand them over, and the younger Sachs has hired a lawyer specializing in Holocaust restitution cases.

"His passion was to make this available to the world, to expose the world to the art form," said the son, Peter Sachs, 67, of Sarasota. "I don't think they should be languishing in a basement, nor do I think the Germans have a right of ownership, considering the circumstances under which they were stolen."

Hans Sachs spent 17 days in a concentration camp after Kristallnacht. He was freed and fled to America with his wife and son. He was certified to practice dentistry and the family thrived in Boston, and later New York City. He died in 1974.

Rudolf Trabold, a spokesman for the German Historical Museum, said Sachs was represented by the United Restitution Organization, a Jewish aid group, when he filed a claim and was compensated the equivalent of about $50,000 for the lost poster collection in March 1961.

When some of the posters resurfaced a few years later, Sachs did not demand their return, so his heirs have no claim, Trabold said.

Peter Sachs' attorney, Gary Osen, is arguing that whatever Hans Sachs was paid does not matter. Osen notes that the German government has committed to returning property seized by the Nazis to the heirs of the rightful owners, regardless of whether restitution has been paid.

Osen said talks with the museum have not produced results. The government's culture ministry recently offered arbitration before a committee that hears stolen art cases, but Osen said he is prepared to sue the museum to force the issue.

"Obviously, it's ironic that the German museum of history doesn't have much regard for history," Osen said.

Peter Sachs said his parents never told him part of the collection still existed. It was only last year, as the retired commercial airline pilot was trying to find original copies of his father's poster art magazine, Das Plakat, that he learned 3,700 pieces were in the German museum. What happened to the rest is unclear, though the museum said some were removed and auctioned in 1981.

Robert Brown, whose Reinhold-Brown Gallery in New York City specializes in poster art, said Hans Sachs' original collection included lithographs from many of the leading artists of a time when posters were a primary medium to promote cultural events, advertise products and disseminate political thought.

The remaining specimens in the museum are likely worth millions, he said, considering that most poster prints did not survive because they were pasted onto walls.

When the Nazis confiscated the Sachs collection, propaganda minister Joseph Goebbels intended for it to be the basis of a museum exhibit on the art of commerce, according to Hans Sachs' written account of the seizure.

Beyond hanging some in his Sarasota home, Peter Sachs said he's not sure what he would do with the art if he gets it. He can see lending some of the pieces to a museum for display.

He and Osen, a New Jersey lawyer, say they are hoping the museum will release the posters without involvement of the courts.

"For us, it's inconceivable that they would allow Goebbels to have the last laugh," Osen said.