What Fred is mentioning is pretty interesting. There was a group of us studying this set and found the variation in the Frank Gifford card. The variation occurred because Gifford was the sole player printed on both sizes of Post Cereal Grape Nuts Flakes (the only cereal these cards appeared on in the promotion). There was an article on this in Sports Collector's Daily (and a more detailed one in SCD). Have attached a link below because it shows the variation. Lastly want to mention that Fred, as much as anyone, was one of the key group members in figuring all this stuff out.
https://www.sportscollectorsdaily.co...ion-uncovered/