This cover-layer cuff is part of the pair was worn by astronaut Ed White on the Gemini 4 mission in June, 1965, during which he became the first American to "walk in space."
The cuffs were worn over his wrist, where the sunlight would have heated the aluminium locking rings to an excessive temperature had they not been protected by these cuffs. They are made of the same high-temperature nylon as the spacesuit, and fitted in place with the help of a small elastic band.
NASA transferred the suit to the Museum in 1967.
Transferred from NASA - Manned Spacecraft Center