Teardown of Cheap Digital Protractors

I recently bought a "Digital Protractor", as I was curious about how it works. On Amazon, the price was about 16 USD.

So here is a visual teardown,  in 4 easy photos.  :-)

I was hoping there would be a hidden data port, similar to what is found on Digital Calipers, but no such luck.  The basic mechanism its similar: as circular track instead of a linear track.