Four Piece Jig Saw Puzzle

Patented K. Walker & designed with H. Nelson, made by Binary Arts, circa 2000.
(four plastic pieces, 4 x 4 x 3/4 inches assembled)

The four pieces do not simply come apart as it appears they might; careful positioning and twisting is required; here is the solution that was sold with the puzzle:

Further Reading

Walker Patent, from: - patent no. 5,409,227