KMS Industries, Alexandria, VA, 1968.
(plastic, 1.75 inches;
directions are in the bottom)

Each of the eight cubes has three colored rods going through it, one in each of the x, y, and z directions (four of the cubes have a red, blue, and white rod, two of the cubes have two reds and a white, one has two reds and a blue, and one has two whites and a blue). Take the eight cubes out of the case and arrange them in a single 2x2x2 cube to make continuous rods of the same color passing through it: