Back when football players did not wear numbers on the front of their jerseys to identify themselves, they sometimes wore numbers on the front of their jerseys to identify their class.
It was not until the late 1920s that players wore numbers on the front of the jersey to distinguish themselves. (Players first wore numbers on the back of their jerseys in 1905, but they were few and far between until the mid-1910s.)
Until the late 1920s, numbers on the front of football jerseys often designated their class team, particularly the freshman class team, with the numbers representing their graduation year. Class jerseys made sense before the rise of intramurals after WWI when class teams often played one another in round-robin tournaments which generally excluded players on the varsity squad. Moreover, freshmen were ineligible to play varsity football at many schools. Instead, they played on a squad overseen by the freshmen coach, and besides playing freshmen teams from other schools, some schools allowed them to play in the interclass tournament as well.
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