"But - just in case the dood's right: I wonder what he makes of the extended "arm" on the Swastika's northeastern side. Perhaps some sorta hook which y' catch it with when it returns???"

Ah, that's easy. Its a cord that's wrapped around a small spindle at the center of the boomerang. You slip the loop in the cord over your wrist, throw the boomerang and then as the cord unwinds from the spindle it imparts considerable extra spin, making the boomerang more deadly and able to travel much further.
;o)