With OpenSCAD I've made a 3D printed rotatable polariser for my microscope - https://github.com/anfractuosity/polarisers

I used these two polarisers in my microscope and a magneto-optical sensor (which exploits the faraday effect), to visualise magnetic field lines of a magstripe card - https://www.youtube.com/watch?v=c8nM4Z-hkTw

I intend to try to use with a floppy disk, however it's not currently working for that.