This strange device is little more than a small bronze orb with a lens. It functions in much the same way as the Periscope Eye except that it is able to move (how it does this is unclear). Although it isn't used in any of the Thief games, it was made at least as early on as Thief Gold. It seems to share some ties to Mechanist optics technology and may be the central component of the Watcher. One peculiar feature of the clockwork eye is that it does not look directly at Garrett, but instead nearly 90° to the left of his position.
There are two books of records in the Eastport Mechanist Seminary, both making reference to "clockwork spy cameras", which may mean the same machine.[1][2]