The Calibron 12 puzzle was designed in 1933 by the son of Thomas Edison, Theodore Edison.
The aim being to fit the 12 pieces into the opening. There is only one solution and this puzzle is rated a level 10 being extremely difficult.
A fun puzzle to play around with as you always seem to get quite close!
This version comes with a wooden cover on top and the pieces are made from at least four different kinds of wood.
The puzzle comes unsolved by the solutionis included.