Ryan NYP Cockpit Periscope Viewport Dual-Frame Calibration Strip (1927)

Two-frame contact strip showing the pilot's sightline through the periscope viewport above the cockpit instruments. — Ryan NYP Cockpit Periscope Viewport Dual-Frame Calibration Strip (1927) · Donald A. Hall Estate Collection

An archival technical test strip consisting of two photographic frames documenting the pilot's forward line of sight through the retractable periscope. Mounted directly above the center of the instrument panel, the rectangular periscope aperture enabled Charles Lindbergh to observe the horizon and runway past the obstructing 425-gallon fuselage fuel tank. The frames record mirror reflection alignment relative to the engine tachometer and magneto controls.