The French know jewelry. With an historical pedigree from Cartier · Chaumet · Boucheron · Chanel · Dior · De Grace · Breguet, yessir, France has a lock on luxury baubles. On a recent Louvre excursion I spent time in rapt appreciation of the magisterial collection of Crown Jewels enthroned in three showcases in the 17th century gallery of Apollo. From the crown of Louis XV to the Le Régent …