It is a Model of 1902 as it has the rounded butt. The Model of 1905 is mechanically identical but has a square butt. SN 1322xx would date its likely shipment to 1909 or possibly 1910 (I list nearby SNs as shipping in both years). It has probably been refinished at some time and the grips are not original, and not made by S&W. Don't worry too much about what ammunition you use, but it is best to stick with using ammunition with lead bullets. The dual-caliber barrel stamping refers to both the .38 Special and .38 Long Colt rounds. The .38 Long Colt is slightly shorter and less powerful than the .38 Special, and was the official U. S. military revolver cartridge of that time. It is also obsolete.