Hi Steve - My favorite pistol! Clearly made in 1957 according to the "Catalog." 1957 serial numbers were from K288989 - K317822. These numbers covered models 14, 15, 16. 17, 18, 19, 48, 53, 66, 67 and 68. Your revolver is a "Model 18, K-22 Combat Masterpiece." This is a square butt K frame...