This is the second prototype of the Kellett XR-8, the XR-8A, which had rounded tailfins. It had two-bladed intermeshing rotors first, but these were replaced by three-bladed rotors soon. In a sequence of photos by Rudy Arnold, it is flagged down by a Philadelphia motorcycle cop at a 25 mph speed limit sign - much the same joke as seen in photo 363024. Flying the troublesome Kellett helicopters was not fun at all, but it is not clear when both XR-8s flew for the last time. Photo by: Rudy Arnold / Smithsonian Institution