Late Cold War-era thermal flash protection window designed for use in the cockpit of the Rockwell B-1B Lancer, measuring approximately 10.5″ x 7.75″ x 2″, with labels on the bottom: "EDU-4/A, Ser. No. 86L0348, NSN. 1680-01-225-4042" and "Window Thermal Flash Protective, Des. Act. 07878/14213, Mfr. 61923, Cont. F33657-85-C-0330, Part 8211550-10." The device has an on/off toggle switch at the bottom: when no power is applied, the window is opaque; when energized, the glass would be clear. Phototransistors sense a nuclear blast and cause the window to become opaque, protecting the pilot from flashblindness; as the nuclear flash decays, the window automatically starts to clear.
