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.