Although not sold in the market, but it is definitely that the small astronomical instrument is a goodie. Inspired by the planet show home, the mechanical model which shows the relative position of the moon is called Moon Phases.
This astronomical instrument made by Yingjie Bei or commonly called Yifan Hu, a student from NYU. This tool serves to show the phases of the moon on a particular day from the perspective of the northern hemisphere.
If you want to know the phase of the moon in a specific year, you can input the desired date. And the mechanism of the tool will display the phases of the moon on a miniature scale.
This tool is a rare and amazing tool. With this tool, you can understand conceptually how the phases of the moon operates and the relationship moon in the solar system.