This is the second iteration of the protractor I made some time ago. Protractor by JohnMartin | Download free STL model | Printables.com
This version is made to print flat with multi-color but there is an STL to print engraved lines and numbers. The old version was embossed, and I like this better. I also redesigned the arm and the knob for better retention, and I added positive stops at 45-degree angles. It's the same size as the original but a little thicker. I've heard that's better.
As a dumb-luck side effect, the stops help keep it from moving around while storing it.
The author marked this model as their own original creation.