Someone mentioned the lettering on the jerseys. The player's names were done in the same type of font that Bama used during the timeframe of the 315 game in 1981. If I recall, Coach Bryant didn't have player names on the jerseys until about the '80/'81 season, and that's what they looked like.
I didn't notice if the style of the jersey numbers was like the old ones. I'd have to go back and look at the old games to tell. It would make sense that they were if they cared enough to get the player name font correct.
All in all, a VERY subtle tribute, and it was very fitting to honor the 315 game and CPB.