A naviculometer is used in foot sizing to measure arch height. This is a rough clone of https://purelycustomfit.com/product/naviculometer/
This can be used with a Brannock Device to get valuable information about a foot as an aid in proper shoe fitting.
How to properly use these things is outside the scope of this description. If you don't know what a naviculometer is, you probably don't need one. The markings are the height above the floor in mm.
The red and white version in the photos is an earlier prototype done with a filament change for increased contrast on the numbers. (The blue spots on the white face are painter's tape which didn't cleanly release from the print) The pink version is the final version available here, I just didn't bother with the filament change.
Filament material can be about anything you want.
It is designed to print face down so the numbers come out as easy to read as possible. No support is needed.
You can use an M600 gcode command inserted before the first layer that doesn't have the printed in numbers for contrast.