Details...

• Character: Missy
• Actor: Michelle Gomez
• Show: Doctor Who
• Episode: 9x01 - “The Magician’s Apprentice,” 9x02 - “The Witch’s Familiar"
• Brand Product : custom cameo brooch based on antique
• Buy:

  Cream and tan large cameo with Artemis/Diana facing right in a thin silver frame. The one used on screen is probably a replica since the details are much simpler than similar antique designs.