This is the outer glass assembly for the window in the left hatch of the Gemini XI capsule. Gemini XI, with astronauts Charles Conrad, Jr. and Richard Gordon, Jr., flew a four-day mission in November 1966. The outer glass assembly had a single pane. Corning Glass made the panes of both the inner and outer assemblies from Vycor, which was 96% silica. NASA transferred this object to NASM in 1969.
Transferred from the National Aeronautics and Space Administration