I'm a STEM tutor and am currently designing an affordable set of designs for an at-home physics experimental course. This is a first piece in series, the angle mount for optics experiments.

Model consists of two parts: the main dial and the vernier. Sights on a ruler housing allow for its positioning on the given target (v1 is mostly the same, but with a hole instead of sights). Vernier allows for positioning with +- 0.5 degree precision. Three M4 holes are meant for mounting of an equipment. To position two rulers in a parallel direction place a straight ruler touching both dials and rotate them to touch at the same position.

Two 5x2 round neodymium magnets are required to hold the pieces together. I recommend gluing one of the magnets with CA glue, then covering it with a scotch tape and sticking the other magnet to it. Then apply glue to the second part and assemble the device, allowing the glue to set. Tape prevents the parts from sticking together. 

Printed with PETG at 0.2 mm layers

For contrast use two colors. I've set the change to 51st layer for ruler housing and 19th layer for vernier. As letters and dials are embossed on the housing and debossed on the vernier you can print both parts with only 2 filament changes, still getting the same color palette for both parts.