 The Illinois State Police adopted the Model 39 in 1968, an action which helped ingratiate semi-automatic pistols with law enforcement.This publicity helped commercial sales and set the stage for the more acceptable Model 59 with its high capacity magazine at least in undercover or detective police use where the DA feature (and the larger magazine capacity) was considered by many to be superior to single-stack semi-automatics and revolvers of the time.A modified version of the Model 39 with a wider grip frame to accommodate a 14-round magazine was used by Naval Special Warfare units during the Vietnam War.