An antiques dealer who sold a rare African mask for $4.6 million won a legal battle with the elderly couple who sold it to him for $165 without realizing the treasure’s actual worth.

A French court has rejected an appeal by an elderly couple who were paid €150 ($165) for a rare Gabonese mask that later sold for more than €4 million ($4.4 million) at auction.

The dealer paid the €150 ($165) for the precious Ngil mask, which was made by the Fang people of Gabon, before sending it to auction where it fetched €4.2 million ($4.6 million), following ...