"Prototype or copy"? I guess there's not much difference between the two.
We need Father Knows Best to light his pipe, put his hand on the seller's shoulder, and give these words of wisdom:
"Son, it's a cheap Stingray copy BTS (Beat to Poop) bike. The crank arms are bent because the poor kid who owned this pile packed on weight but never got a new bike. $10 is too much. Any amount of money is too much. Maybe some guy will trade you a pair of lightly worn socks for it".