Pre-Coryell NFL
The pro set was the default NFL scheme prior to Don Coryell. While it is more of a formation, the underlying philosophy of the pro set was based on becoming more successful when a team was forced to pass by providing 1 or even 2 backs to help protect the QB. Prior to Coryell, the pro set was generally a running offense that used play action fakes to set up deep passing attempts when defenses stacked up vs the running game.
The pro set features a TE, 2 WRs, and a Halfback and fullback, often split behind the QB. While QBs can take a snap from the center from the shotgun position, in general the pro set QB takes the ball under center to allow for better play action fakes to the running back. Offenses tended to be ball-control, grind-it-out style offenses. In 1978, the contact from defenders on receivers was minimized with the passing of Mel Blount Rule.
Read more about this topic: Coryell Offense