Self-Locking Building Bricks

My son was writing an essay about the creation of certain building blocks, and we learned about the original Self-Locking Building Bricks that they were based on. He asked me to print some of these originals to display to his class, so I threw together a quick design just based on eye-balling some pictures. These are not intended to be accurate replicas, since I don't have any details on the original dimensions. 

These are a little large, coming in at 5cm³. They needed to be big enough to show to a classroom, and I think they're the perfect size for a simple toddler building block.

I haven't tested the tolerances with smaller (or larger) sizes, but if someone wanted that I could play around with different sizes and add some profiles.