9.25x4 Envelope filled out and signed in black ballpoint ink by John Cage. Folding crease down the center. In very good condition. 

(1912-1992) John Cage was an American composer, artist, and music theorist. A pioneer of indeterminacy in music, electroacoustic music, and non-standard use of musical instruments, Cage was one of the leading figures of the post-war avant-garde. Critics have lauded him as one of the most influential composers of the 20th century.

Comes with a full Letter of Authenticity from Todd Mueller Authentics.