Many articles on the Belichick/video camera kerfuffle contain references to the 1951 NY Giants who, in a recent book, were said to be stealing signs using a telescope located in the outfield and a buzzer for communication. For example:

The Patriots' three Super Bowl wins will now always be suspect thanks to a coach who not only refuses to play by the rules but also refuses to acknowledge he did anything to break them. But how about the pennant won by the 1951 New York Giants, who were using a telescope-and-buzzer system to steal signs at the Polo Grounds where Bobby Thomson hit the “Shot Heard 'Round The World?”

Although there is no way to prove that the Giants' sign stealing didn't affect the 1951 pennant race, I have a forthcoming paper showing that most of the Giants' improvement after they started stealing signs came from better pitching not better hitting. Indeed, the Giants scored nearly a run less (0.85) in home games after July 20 than in home games before July 20. (July 20 is the day the sign stealing scheme started according to Prager.)

This is not to say that Belichick was not stealing signs or that his sign stealing had no effect. (Yesterday's results--Patriot blowout of a good San Diego team and another Jet loss--suggest stolen signs had little to do with the Pats thumping of the Jets.) It does mean that writers should think twice about asserting that the Giants stole the pennant in 1951.

ADDENDUM: An astute reader asks if my results for the 1951 Giants might reflect a general trend of improving pitching over the course of a season. Two answers. First, my analysis of Giant hitting controls for the quality of the opposing team's starting pitcher. (I use ERA, but I also tried more sabermetric measures like HR rate and BB rate.) Second, the trend in 1951 might have been different, but the current trend is for pitching to deteriorate over the course of the season (here; scroll down to the section labeled "Months").