Football helmets have evolved quite a bit over the years. And in the case of the Pitt Panthers, you can track that evolution on the back of their current helmet.

Each Pitt helmet has five little decals on the back, showing the progression of the school's helmets, from the old leatherhead days through the team's more contemporary looks. Think of it as a little Pitt timeline.

Lots of schools give out merit decals or pride decals as a reward for good plays, of course (Illinois is using some shaped like the state of Illinois this season), and I mistakenly thought that's what the Pitt helmet decals were for. But according to a tweet from the team's equipment manager, they're actually a salute "to the rich history of Pitt football."

Nice -- an impromptu history lesson played out in the course of five stickers. An exhibit of helmets on helmet. Wouldn't it be cool if more teams did this?