Calibron 12

Calibron 12. The objective is to fit all the  pieces in the large square opening. There is only 1 solution and it is very difficult to find.  We packaged the puzzle unsolved, but the solution is provided.  In the frame I made an extra space to hold one of the pieces so that we could package it unsolved.  Our version is made from precision cut woods with at least 4 different woods in each puzzle.- Calibron 12.