Aha!
definitive proof of the boomerang throwing theory. the 'sighting notch' to ensure pin-point accuracy for long range throwing. the wood grip of course being used to catch it on it's return after it's mission of severance.
they left off showing the opposite side which contains the parachute and landing gear in case the thrower misses his retrieval catch. one should of course not catch it by the blade, it upsets the gyroscope, and may cause tumbling...
