Four puzzle pieces assemble into an interlocking octahedron. This puzzle is similar to my "Screwy Octahedron" except it uses three identical screw-shaped pieces. This puzzle would be difficult to make in any way other than 3D printing due to the complex 3D shapes of the pieces. Assembly requires coordinate motion.
Notes: Uses 13mm diameter spheres. Screw piece have offset 0.1mm, Y piece has offset 0.0mm.
Only a single copy of this puzzle exists. It is quite expensive and I am not sure if the tolerances in metal are good enough to reproduce it reliably.