BERLIN (AP) — Germany’s top federal appeals court is set to rule Friday on whether a Berlin museum must return to a Jewish man from Florida thousands of rare posters that were seized from his father by the Nazis.

Lower courts have ruled that Peter Sachs, the son of collector Hans Sachs, is the rightful owner of the vast collection of advertisements and political propaganda dating back to the late 1800s, and now believed to be worth between euro4.5 million and euro16 million ($6 million to $21 million).

What the Federal Court of Justice in Karlsruhe must decide is whether the law provides for Sachs to get the posters back from the German Historical Museum, a decision complicated by their unique and tumultuous journey through more than 70 years of German history.

It said last month it must “review and clarify” the situation, in which the posters were stolen from Germany’s leading private collector by the Nazis’ Gestapo, moved on to the possession of communist East Germany, then to the Berlin museum after reunification — and now through some five years of legal battles.

“Every court that’s looked at this says that Peter Sachs is the owner of the collection, so from our standpoint the worst case scenario is they say he’s the owner of the collection, but we don’t have a method to help you free your property,” said New Jersey attorney Gary Osen, one of the lawyers representing Sachs.

“It’s just a bizarre nether-world situation.”