Circa 1967, bell Aircraft produced a design for a tiltrotor VTOL aircraft that would be quite similar to the V-22 Osprey of 20 years later. the Model 266 had two T64 turboshaft engines, one at each wingtip. Each engine drove a three-bladed prop/rotor that could be tilted to provide vertical or horizontal thrust, with cross-shafts making it so that the aircraft could power both props in the event that an engine were to go out. The overall configuration was much like that of a spindlier V-22 with a conventional tail. The basic role was as a troop transport for the US Army.
The full-rez scan of the art has been uploaded to the 2022-02 APR Extras folder on Dropbox. This is available to all $4 and up Patrons and Subscribers. If you would like to help fund the acquisition and preservation of such things, along with getting high quality scans for yourself, please consider signing on either for the APR Patreon or the APR Monthly Historical Documents Program.