Believe it or not the frame was made by Shelby, circa 1938. Along with the more well known line of Airflow frames Shelby had a second pattern frame, available in both straight-bar and parallel curved bar (rainbow) versions. This frame is fairly uncommon and there is some (unproven) speculation that at least the rainbow version of the frame may have been available as a MW Hawthorne. A rainbow frame is known to exist with a quad-plate crown fork like the one on this bike but the few Shelby catalog pictures of the frame show it with the more standard forged crown Shelby fork. There is no known tank for the rainbow version but the frame you have does have a companion tank, specific to the frame, that I have only seen twice on eBay in the last ten years.