Chakshu Upanishad Pdf Access

Need to verify some facts: The name "Chakshu" is from Sanskrit, so "chakshuḥ" (चक्षुः). The Upanishad is attributed to which Vedic school? If it's from the Rig Vedic school or another, but perhaps it's not clear. Some Upasanas might be attached, but minor Upanishads might not have clear lineage.