The Treasure Scope is an upgrade for Rouge the Bat in Sonic Adventure 2 and Sonic Adventure 2: Battle. It is a GUN-made scouting device that allows Rouge to see and interact with invisible items, such as item boxes, rings and Springs. It can be used by selecting it in the action window and the pressing the B button, but will be taken them off whenever Rouge jumps. They are the equivalent to Knuckles the Echidna's Sunglasses.
When beginning the stage, head to the C-Block of the area (on the right) and climb up to the second floor, the "Yellow" floor that is attached to the wall. On this floor you will find an Ancient Shrine where you must play the Mystic Melody. This will make several platforms appear which leads over to the opposite wall, where you will find some iron containers blocking a gap into the wall. Use the Iron Boots to destroy them and head into the gap which leads into a hidden room where the Treasure Scope is located.
Rouge also uses the Treasure Scope in Fly Spy to find the world's largest diamond in a museum.