Cool bike! I personally think that was a carefully built Schwinn Krate/stingray cross, the comment about the overload is true, and that certainly is odd. If someone did build it, they did a a great job. It could be a five speed stingray original, I didn't know such a thing existed. I would estimate it to be worth $200-300 but that is a ROUGH estimate, I don't closely follow the stingrays. Best of luck!
Chris S.