A remix of tvputten's tokens designed for dualstrusion printers so you can get a nice crisp contrast between the disc and its number, without painting. I recommend a white bottom and either black or red tops to match Catan's discs.
As with tvputten's discs, these lack the letters. Print as many as you need for either the 3-4 player game, or 5-6 player game, then use a Sharpie to write the letters on the back. That way you have them for setup but not in the way during play. You can also use the same tiles for both 3-4 and 5-6 just by having both letters on the back (some tiles will be used only in 5-6 of course).
I've included the SketchUp files for further remixing. Note that the import process from tvputten's stl makes a messy SketchUp file, and while I did some cleaning, they're still not as nice as if I had the original source (or had done it from scratch).
Yes, all the "bottom" pieces look the same. Why the duplication? To make sure each bottom and its corresponding top line up perfectly when you merge them. I couldn't easily make sure all the tops were at the exact same starting coordinates, and ReplicatorG gives me no opportunity to align parts when merging (maybe other software does), so this is the surest way to get a good merge.