This thing is a camera! Specifically a Fusil Photographique, or “rifle camera.” It was built by Etienne-Jules Marey, who used it to photograph birds in flight, and it’s been called the world’s first portable motion picture camera.
Pretty stylish, right? Gives a whole new meaning to the phrase “point and shoot.” You can read more about Marey and his contemporaries here and here. (Thanks to the inimitable Ben Simington for the heads-up.)