Mirrored earrings come as a pair. Using one earring you can see the room where the other earring is currently located and vice versa.
Mirrored earrings can be purchased as a pair in a small earring box from Niknax.
gaze [into] earring
This shows you the room where the earring is even if it is in a container, a player or a npc:
You gaze into the mirrored earring. You see a place: The land is lit up by the eerie light of the first quarter moon. Weaver Street curves here as it travels to the west and northeast. A thick hedge looms to the north, blocking access to Nap Hill. Along the south side of the street huddle a group of old flats starting to go to seed. From the look of things, many of the residents tend to work late into the night. With few people about, this seems to be a quiet part of the city, perfect for getting mugged. It is a damn cold backspindlewinter's night with almost no wind and scattered puffy clouds. There are two obvious exits: northeast and west. Player and a short troll are standing here. A street lamp is emitting a grimy light here.