Cover ornamented with rubber stamps in black ink: sender's return address, "BRAIN CELL RYOSUKE COHEN" logo. Rubber stamp in yellow ink: "ceLL". Rubber stamp in green ink: "PRINTED MATTER ONLY". Rubber stamp in blue and red ink: circular design with mushroom cloud silhouette, "NO MORE HIROSHIMA", and "RYOSUKE COHEN". Rubber stamp in purple and orange ink: cartoon sumo wrestler. Typewritten call for "seal or stamp" art for Brain Cell project on reverse. Poster enclosed. "MAIL ART NETWORK FOR CHILDRENS [sic] OF THE WORLD SHOW", list of participants.