I had always been told it was pre-WWII. Pre K? But what is the model of this revolver? Could it possibly be a Prewar K-22 Combat Master Piece.
No, it's a postwar K-22 Target Masterpiece. A prewar gun would have:
1) Tapered-top non-Magna walnut stocks with gold or silver medallions. Granted, stocks can be swapped. However, if it were prewar, it would also have...
2) A long-action "hump back" hammer. The hammer in the picture is clearly a short-action hammer.
3) A smaller non-micrometer rear sight. The big adjustment screw gives yours away as a postwar micrometer sight.
4) A smaller-diameter barrel with a more tapered profile.
FWIW the prewar name of this gun was the K-22 Outdoorsman. Here's a thread from the S&W forum with some good pictures of a correct one:
BTW don't be upset that it's not actually prewar because the early postwar K-22s are quite sought after. They have sharply climbed in value just in the past year or so.
FWIW a Combat Masterpiece has a 4" barrel with a Baughman Quick Draw ramp front sight rather than a 6" barrel with a Patridge front sight.