The S&W K22 being a four screw simply ID's the time frame of the gun as from 1956-1960. S&W changed from using a screw at the top of the sideplate to using an internal tab to hold the sideplate to the frame at that point after 1955. In 1961 S&W changed the way the cylinder bolt was held in the frame to not have to drill & tap a small hole at the front of the trigger guard and fill it with a screw. This is the "fourth" screw of a 4-screw gun, the other three are on the sideplate.
The Colt OMT is pre-WWII, as after the war they changed the name to Officer's Model Special for several years, then changed it again to Officers Model Match. This is the same action and frame size as the Python, 357 Magnum and Trooper model revolvers. Like the Python, the OMT was a top of the line premium revolver.
Both the K22 and the OMT were intended for 22 caliber Bullseye target shooting and are roughly the same size, the K22 being slightly smaller. Pricewise, if both guns are shooters, and not near NIB collectables, the K22 should be around $350-400 and the OMT around $400-500. These prices are for guns in excellent condition with some, but little, wear of the bluing on the muzzle of the barrel and high points of the cylinder. In near NIB condition, the K22 will be $500+ and the OMT $750+; depending on exact condition of the gun, the condition of the box and associated tools and paperwork being present.
