In 1968 Corita did a series of 26 screen-prints, one for each letter of the alphabet. She called the series the "international signal code alphabet". Each letter espoused a theme that was important for her, such as: "a is for astrology", "b is for be-ins", "c is for clowns", "d is for digging it", etc.
This image, done in the U.S. flag's red, white, and blue, is the letter "t" which the artist titled "t is for two". The formal edition is not stated. It is illustrated in color, with the other letters of the alphabet, on pages 176-77 in the publication "Someday is Now - The Art of Corita Kent", ISBN: 978-3-7913-5233-6.