This is an interesting letter found on the Heritage Auctions site. It is undated, but it is obviously from sometime in the 1960’s. Back then, players throwing the balls into the stands happened frequently enough to have been a problem that the team (and perhaps the league) wanted the players to stop doing. It doesn’t say so, but the cost of replacing the footballs was probably also a concern. And they didn’t cost over $100 as they do now.