Front and backs clearly show two different printings
Card images and below comments attributed to Brian Bigelow
 
1. FRONT - differences in the athlete's size, face and hair, thickness of the hammer handle 
2. FRONT - type style and placement of school name
3. FRONT - book pages on seals (one has letters; one doesn't), stripes are different 
4. BACKS - the "No. 11" (at the top) - difference in type shape ("serif" and "sans-serif") 

All of the T6's have these kinds of variations