Patented by Andy Turner, made by Eric Fuller 2010.
(Oak box 2.75" square by 2.1" high, Bubinga puzzle 2.2" square)

Don't read any further; have some fun first. This puzzle is quite hard until one sees the trick, and then it is almost impossible to forget how to solve it.

The two 1x2 pieces have double holes at one end that naturally entices one to use them, but in fact these two faces butt against each other in the unique solution (no pegs going between them), and then the puzzle solves easily. Here are four photos in sequence of assembly: