It took just four minutes for a group of audacious thieves to pull off what may have been one of the most daring crimes in modern art: the theft of Napoleonic-era jewels from the Louvre in Paris on the morning of October 19. The heist, which took place while the museum was open to the public, involved a variety of jewels once owned by members of the French monarchy, including an emerald necklace and earrings that Napoleon gave his second wife Marie-Louise for their wedding. Now, questions are raging about how masked men could successfully evade security and nab priceless...