The scale is in centimeters? Correct?
Any chance this is a small, portable, rudimentary scale or balance?
On the first picture, it appears that the rotating portion will not travel 360-degrees as there is (what looks to be) a stop in the perpendicular axis.
In the photo, it looks like one of the arms might have been "stuck" in this position - just going by the dirt and grime pattern left behind.
Perhaps that (lack of 360-deg movement) is a clue to its function?