I printed these face down in two parts using the filament swap method. The details of the characters are quite small, you may need to print it larger or increase the layer thickness or flow rate to get it to stick. 

Drop the disc file and the character file in a slicer, they should align perfectly. There is a small ring around the characters - it is very thin and should not slice for printing, it is only there for proper alignment in the slicer.

Additionally I've included files with the characters extruded on top instead, these can be printed face up with a filament swap or the characters can be painted later.

(The characters on the photo are mirrored, this is fixed in the files but I have not taken a new photo yet).