This little address book appears to have been used by William partially as a "little black book", partially Navy buddies, and it was also used to keep track of his addresses as he was transferred from place to place. 

He entered the Navy Nov. 23, 1943 and went to boot camp in  San Diego, CA.  In Jan., 1944 he went to AOM school in Norman, OK. In May of 1944 he was transferred to the Naval Air Station in Almeda, CA.   From there he was sent to Vernalis, CA, Monterey, back to Vernalis, then to turret school in Jacksonville, FL (he was there in May, 1945), and finally Eaton, NC.

This William David Casto has been identified by Ina Tuft as the son of Everett Grant Casto and wife Maud Velma Radley.  William was born 9 August 1925 and died 31 August 2000 (SSDI).