O.K. Model chambered for .22, .30 and .32 rimfire cartridges. Barrel 2.125" or 3.125" on .32 rimfire. No extractor. Functions as 1st Model. Frame plated brass, with flat sides. Barrel found blued or nickel-plated. Grips are rosewood. Markings same as on 1st Model, but located on right side of barrel. Top of barrel marked "O.K." Approximately 5,000 manufactured between 1863 and 1870. About double values for rare square butt variation.