"At a professional event in 1951 the forehand drives of a number of players were electronically measured. Pancho Gonzales hit the fastest, 112.88 mph, followed by Jack Kramer at 107.8 and Welby Van Horn at 104. Since it was generally assumed at the time that Segura had the hardest forehand among his contemporaries, it is possible that he was not present at that event. "
Did they have accurate radars in 1951? There has been radar disputes all over serves here in the forums, so I'm not sure about the radars in 1951 (or if they had any).