The Smith & Wesson Model 640 is a descendant of the “J”-framed S&W Model 40 and was first introduced in 1990. The Model 640 differs slightly from its ancestor, the Model 40 (also known as the Centennial), in that it features a stainless steel frame. The Model 640 was only offered as a .38 Special revolver until 1996 when it offered in the .357 Magnum caliber as the Model 640-1. The S&W Model 40, 640, 640-1 and all similar variants are ideal pocket firearms due to their distinctive “hammerless” feature. While the phrase hammerless is misleading since they contain enclosed hammers, this feature allows the user to safely fire from within their pocket without worrying about the hammer snagging. It also alleviates any worry that lint or other elements may breach the firearm, rendering it disabled. As sales records from S&W show, the Model 640-1 and its variants are tremendously popular revolvers among those seeking a reliable backup firearm or personal defense weapon.