A family is suing the U.S. Mint, saying it illegally seized 10 gold coins that are among the rarest and most valuable in the world that the family found among a dead relative's possessions.

The lawsuit, filed Tuesday in U.S. District Court in Philadelphia, accuses the Mint of violating the Constitution and breaking federal forfeiture laws by refusing to return the 1933 "double eagle" coins to the family after it handed the coins over to have their authenticity confirmed.

Plaintiffs Joan S. Langbord and her sons, Roy and David, are seeking the immediate return of the coins, said their attorney, Barry H. Berke.