“This is a monarchy,” says the couturier Norman Hartnell to the young Queen Elizabeth. “And if you’ve got it, flaunt it, I say.” And flaunt it Winterthur does. Following up on “Costumes of Downton Abbey,” the biggest hit in its 67-year history, Winterthur is now showing 40 memorable costumes from seasons one and two of the Netflix series The Crown. The tutorials on orders, medals, tiaras, and pearls will forever change your understanding of British royal dress. —L.J.