Peephole Ring

A Peephole Ring is a plain silver band, with an image of an open eye that appears to be a centimeter inside the otherwise opaque surface.
The ring grants no benefit or effect from simply being worn, but instead must be removed and placed against a surface to function. When placed on a wall or similar surface, it allows the user to look through it as if there was a ring-sized hole through the wall, through up to 1 foot of wood or 6 inches of stone. Any amount of metal prevents it from functioning. If the wall is too thick, the ring will remain inert.
The peephole is an illusion, so objects cannot pass through. The ring gives off a faint aura of divination.