.38 Special. This model has been in production in one configuration or another since 1899. It was always the mainstay of S&W line. Originally known as .38 Military and Police Model. The Model 10 is built on the K, or medium frame, and was always meant as a duty gun. Offered with 2-, 3-, 4-, 5- or 6-in. barrel. Currently only 4 and 6 in. are available. Round or square butt, chambered for .38 S&W Special. Offered in blue or nickel-plate, with checkered walnut grips. Model designation stamped on yoke on all S&W revolvers. The model 10, with many other modern S&W pistols, underwent 14 engineering changes. These changes may affect value of the revolver, and an expert should be consulted.