I received inspiration for this project from a Turner's Cube: https://makezine.com/2010/10/18/the-turners-cube-classic-machinists/
I thought about making a Turner's Icosahedron, and then why not add numbers to make it a D20? This is the result. A beautiful work of regular symmetry!
The printed item in the photos is about 30mm across the faces. It took about 2h45m to print and another hour of post cure time at 50 microns/layer.
At higher resolutions of 25 microns, the print time would drastically increase.
Printing this model on a SLA printer is almost a requirement if a small size is desired. For FDM and other methods the 1:1 size or larger would be required.
When adding supports for the SLA process be sure to omit them from the thinnest sections to avoid damage by support removal.