Basic idea by Stewart Coffin, made by J. Storer 1989.
(top: purple heart with dowels, 3 inches;
bottom: rosewood with dowels, 2.25 inches)
Like the Cubes and Pegs puzzle, except here 4 pieces have one form and 4 the other (the pattern of pegs in the soluton to this puzzle is different from Coffin's Book Fig. 193):