Donald Mellein was storing 110 gold coins in one of the boxes. The FBI initially said it did not have the coins, but Mr. Mellein's legal action resulted in the agency acknowledging it did have 47 of them.

The FBI returned the coins but still has not given back the other 63, which are worth an estimated $123,419, according to one of the new lawsuits.

"Don's gold coins were completely secure until FBI agents broke open the safe-deposit box looking for property that could be forfeited. Their disappearance can only be explained by the acts or omissions of the FBI agents who broke into the box and rummaged through it. The FBI never should have broken into the safe-deposit boxes in the first place but, once it did, it became responsible for returning everything it had custody of, unless it had a lawful reason to keep it," the suit, filed in U.S. court in California, states.