This is George Hart's reconstruction of a 16th-c. wooden puzzle, currently in the Schloss Ambras Museum. Print out 76 units and reconstruct the original! A full description is available at http://www.georgehart.com/rp/torzle/torzle.html.
I've scaled the basic unit to be a reasonable size in millimeters. You may want to go somewhat smaller to reduce print times.
The other files diagram how to assemble the entire piece.
Attribution goes to George Hart, not to myself. Please credit George Hart and include a link to the source if redistributing: