Here, the contents of the queen’s box are revealed. She gave the duke diamond tags, which are studs that would be worn as part of an elaborate outfit. The cardinal knows that the king would be hurt if he learned this information because it feels like a double betrayal of his trust. Not only did the queen give the duke a gift; she gave the duke a gift that was first given to her by the king. If this information were to get out, it would create exactly the scandal that the queen was trying to avoid.