This is a guess but I'd say home-made bullroarer. Many of you have probably played with something similar... a button with two holes, a string run through the holes and made into a single loop. You wind the thing by flipping it round and round, with the button in the center, and then play it by alternatively pulling on the strings, and leting them spin out, then back in, then out, in.... WHIRRRRR WHIRRRRR WHIRRRRR... the scalloped edges might make the sound louder.
The whirring sound they make is fun. I remember Mama seeing one I had made with a HUGE button. "What is that thing?" she asked "An orthopedic yo-yo?" LOL The description fit exactly! 'Orthopedic yo-yo" has been a family joke ever since.
SageGrouse