His pitch selection included a drop curve and an "inshoot", which was probably the modern screwball.[1]
The New York Clipper wrote of Jack Lynch:
Studying the in-and-out curves, rises, and drop deliveries, he rapidly acquired a reputation as an effective and puzzling pitcher...He has complete control of the ball, with all the curves and varying paces in delivery, and is cool and self-possessed.[2]
References
^The Neyer/James Guide to Pitchers: An Historical Compendium of Pitching, Pitchers, and Pitches. Bill James and Rob Neyer. 2004.
^New York Clipper (undated, from the Baseball Hall of Fame Library).