This is a truly amazing work of art and machinery. Built in Geneva by Rochat around the year 1820, these two pistol-like objects are actually tiny music boxes. When the user pulls the trigger, a tiny, realistic mechanical bird pops out of the end. It dances as the musical components play what sounds just like bird whistling.
This video from the auction house Christie's shows how devices work, including internal diagrams. You can skip to 1:45 in the video to see them in action.
via Everyday, No Days Off