These are plex panels which covered an opening cut into the forward camera of NASM's Corona KH-4B camera to enable viewers to see the lens inside. The KH-4B was the last and most advanced camera system used in Project Corona, America and the world's first photoreconnaissance satellite program. Between August 1960 and May 1972, when the program ended, 145 Corona satellites were launched and they produced over 800,000 usable images of the USSR and other nations. Film return capsules containing the exposed film separated from the spacecraft in orbit, reentered the atmosphere, and were retrieved in midair. The Itek-made KH-4B camera was used from 1967 until the end of the program and under ideal conditions produced a ground resolution of 6 feet. The two plex panels were not reinstalled after restoration of the camera in the early 2000s because they were discolored.
The National Reconnaissance Office transferred the KH-4B camera to NASM in 1995.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.