A case for sewing bobbins available in multiple sizes. Included are STL files for the “Bobbins” legend.  Select the STL file that matches the layer height you use for the top box.  Print the legend on the print bed, remove the skirt if any, change filament and print the top box over the legend.  PETG on power coated steel sheet works best for me.  Model printed with 0.6mm nozzle and 0.3 mm layer height and 0.4 mm nozzle woith 0.2 mm layer height should also work.  15% infill.