This is a simple customizable clip-on shelf label placard. If you have OpenSCAD installed, you can open the scad file and adjust the size and dimension of the label directly in the code (the variables are clearly documented). The premade STL files are for a 60mm wide label and a 12mm shelf thickness.

Text is added in the slicer before printing. The recommendation is to "engrave" the text into the front of the label, rather than printing on top of it. For example, in the Bambu slicer you would add text via the text tool, set thickness to 2mm, set an embedded depth of 1.5mm, and then in the object settings for the text entity, right-click -> "Change Type" -> "Negative Part". This should "engrave" the text into the label (default thickness is 3mm) when you slice it.

FreeCAD (v1.0) and OpenSCAD files both made available, as well, as some premade STLs (for 12mm shelf height and 60mm long).