The Smith & Wesson Model 39 is a semi-automatic pistol introduced in 1955. It was one of the first successful double-action/single-action pistols and features a 9mm caliber. The Model 39 is known for its lightweight aluminum frame and a 15-round magazine capacity, making it popular for both law enforcement and civilian use. This firearm has a reputation for reliability and accuracy, with a barrel length of 4 inches. The Model 39 has influenced many subsequent designs in the handgun market, contributing to the evolution of modern semi-automatic pistols. Its ergonomic design and manageable recoil make it suitable for various shooters.