Thanks to Splemsby for the original keychain model. It's a clean model and an easy print, feels good in the hand, just what I was looking for.

Retro hotel keyfob / keychain with a blank face so you can add your own design. You can use 3D modeling software or add a text design directly in PrusaSlicer.

I recommend one of these:

• Microsoft 3D Builder: Edit, Emboss (can also “load” a pattern from any picture)
• PrusaSlicer: open the model, right-click it, Add part, Text
• TinkerCAD: easy-to-use app to edit STL files and add shapes or text to them

Measurements:

The blank face is 2mm thick, and the ridges on top are an additional 1mm thick (3mm total). So I recommend your embossed design should be around 0.4-0.6mm thick. Enough for a filament color change to show up, but lower than the existing ridges. But hey, be creative, do it however you want.