U.S. Department of the Treasury officials insist the $20 Double Eagles were stolen from the U.S. Mint in Philadelphia before the 1933 series was melted down when the country went off the gold standard. They argued that Joan Langbord and her sons cannot lawfully own the coins, which she said she found in a family bank deposit box in 2003.
Langbord's father, jeweler Israel Switt, had dealings with the Mint in the 1930s and was twice investigated over his coin holdings. A jury in 2012 sided with the government.
However, the appeals court returned the coins to the Langbords because U.S. officials had not responded within a 90-day limit to the family's seized-property claim, filed in about 2004.
Family lawyer Barry Berke said: "Congress clearly intended for there to be limits on the government's ability to seek forfeiture of citizens' property, and today's ruling reaffirms that those limits are real and won't be excused when the government violates them."
Langbord, who's in her mid-80s, worked in her father's store on Jeweler's Row for most of her life. Her sons, entertainment lawyer Roy Langbord, of New York City, and David Langbord, of Virginia Beach, Virginia, joined her in the legal fight.
They do not plan to comment on the ruling and have not decided whether the coins will be sold, Berke said.
Sculptor Augustus Saint-Gaudens designed the Double Eagle with a flying eagle on one side and a figure representing liberty on the other.
One Double Eagle, once owned by King Farouk of Egypt, sold in 2002 for $7.6 million, then a record for a coin. Its later owner, a London coin dealer once jailed by the U.S. over it, split the proceeds with the U.S. in a deal brokered by Berke.
The Langbords offered the government a similar split but were rebuffed.
The family had taken the coins to the Secret Service in Philadelphia to have them examined, Berke said.
"They authenticated the coins and said, 'Thank you very much. We will now be keeping them,'" he said.
The Mint struck nearly a half-million of the Double Eagles in Philadelphia in 1933 but never released them. They were melted into gold bars after President Franklin D. Roosevelt abandoned the gold standard.
While prosecutors argued to jurors in 2011 that Switt must have stolen the coins with help from a Mint insider, Berke said he could have traded his scrap gold for them.
The U.S. Department of Justice said it was reviewing its options after Friday's ruling. A Treasury spokeswoman had no comment.
Switt admitted to the Secret Service in 1944 that he had possessed and sold a set of nine other Double Eagles, which were recovered and destroyed. The surviving Farouk coin is believed to have been a 10th coin from that batch.
The Mint sent a pair of 1933 Double Eagles to the Smithsonian Institution for its U.S. coin collection.