The aligned holes in the piece-pair containing the START piece show the letter "C". Those on the pair containing END give the letter "E". The other two pairs show "U" and "B", leading to the final answer "CUBE". Of course, 8 is a CUBE, and the geometric dual of the octahedron is also a CUBE.
I hope you enjoyed working this puzzle!
Pavel Curtis
Pavel's Puzzles
High-quality mechanical puzzles, direct from the designer!