This compass is what was left over of a imitation ivory folding opera glass made at the 1890's. For a good impression look at the site of Mister Jean Paul Donzey, the Compass museum. com. Here he shows five folding opera glasses (just scroll down  the page) Lots of these compasses I found on fleemarkets. The story was always the same. "This is a military German compass and  it has a signaling mirror."

This kind of instruments are still made for children. It's a loupe, binoculars, compass and mirror.