Royal Silver Medallion
From the Super Mario Wiki
The Royal Silver Medallion is a key item from Wario: Master of Disguise. It is contained within a purple treasure chest inside Poobah the Pharaoh's Pyramid. During Episode 5, the Pharaoh's royal gatekeeper tells Wario to find it along with the Royal Gold Medallion in order to gain permission to meet the Pharaoh. The medallion is in a dark room with spikes on the far right of the pyramid, three floors above the Pharaoh's room.