This thing is from 2012. It's a set of printable models for toy parts that allow interconnecting with a bunch of different construction toys, like Lego and K'nex.

I remember thinking this was pretty subversive and cool back then. My own experience in 3D printing since that time has taught me that there is no way that these parts can ever be printed accurately enough to actually work. It didn't get much traction on the Thingiverse files either.