Perplexing Pyramid Puzzle

This is one of my favorite ball pyramid puzzles. It was designed in 1976 by Leonard Gordon. For many years, Kadon Enterprises sold this puzzle made from injection molded clear polystyrene (see the photos). These puzzles are no longer available but you can read about their history here, and you may find them for sale in places like eBay.

You may find the same puzzle under many different names now. Puzzlemaster has a metal version they call "Kugelpyramide". It is one of the most difficult 20-ball tetrahedron puzzles.

Two pyramids can be built from these pieces. The tetrahedron with a triangular base (hard) and the pyramid with the 4x3 rectangular base (medium). The double-sided base plate allows you to make both pyramids, but need supports. The single-sided base plate includes only the triangular base.