The victim was a baseball player found murdered in 1945 in "Connie Mack Stadium". However, this name was used only from 1953 onwards and in 1945 would have been called Shibe Park.
Set in 1945, a character (Moody Brown) uses the phrase "boys of summer" to describe ballplayers. Although the phrase was originally used in a Dylan Thomas poem, it was not associated with baseball until the publication of the book "The Boys of Summer" by Roger Kahn in 1972.
The Negro League team had players last names and not numbers on the backs of their uniforms. Players last names did not appear on uniforms until 1960 when the Chicago White Sox started using them.