Robert Indiana kept a series of illustrated journals during the late 1950s and 1960s, in which he discusses the development of his work as well as his daily life on Coenties Slip. 

Indiana's journal entry for August 27, 1961, includes a sketch of Mate. Indiana notes that he spent most of the day on the work's base, and that he added the letter "M" to the reverse. He also records that it was a "hot and sultry day, with a constant sun," and that his friend Norman (Fisher) was down to work with J. (his partner, fashion designer John Kloss) and stayed for lunch and dinner.