Stackable Box Toy Free 3D print model

A set of stackable and nestable boxes decorated with shapes and letters.
WARNING: Objects smaller than 45mm are unsuitable for children under 3!
WARNING: Check the material you are using to print is safe for children!
WARNING: Ensure no loose parts or sharp edges once the part is printed!
The boxes nest neatly inside one another and securely on top of each other in purpose made slots. Each box is cubic and 5mm bigger than the last. The sides are decorated with the alphabet, geometric shapes, Makerbot and RepRap logos, and the message I-LOVE-REPRAP-MAKERBOT.
This design is loosely based on the Montessori pink tower. What other teaching aids could we make with our machines? What about a Makers4Schools movement?

I recommend printing the basic set in the Parts List, which is the first eleven boxes from 10mm to 60mm. The first six are all in one STL file and fit in a 100mm print area, and all the rest are in individual STL files. I've included STL files for boxes up to 100mm, but I haven't actually printed any above 60mm.
No support material is required for printing and any fill setting above 10% should work fine.
The OpenSCAD is as flexible as I could make it given the limitations of the language. It is easy to modify the text on the boxes or to start the lettering (or numbering) from a larger box size (say 45mm) if you wanted to create a set for children under three years of age.
The OpenSCAD is designed to work in two ways: output all the boxes (using a loop) or output a particular box. This is all controlled by the ! operator prefix.
The OpenSCAD source uses @tbuser's bitmap fonts, but modified to remove the slash from the zero. Files bitmap.scad and logos.scad also need to be in the same folder as the NestedBoxes.scad.