Duffy added side numerals to Spartan helmets just prior to the start of the 1956 regular season. The Michigan Wolverines also wore side helmet numerals for the very first time starting with the 1956 season. Both teams may have been encouraged by the Big 10 league office to wear the numerals to enhance the viewing pleasure for the growing national television audiences who followed Big 10 football. Duffy retained the side helmet numerals up through the 1964 season as reflected by the number "64" or 1964 season helmet pictured.