I lucked into this 5-screw K-22 Masterpiece in .22 LR yesterday. According to the Standard Catalog of Smith & Wesson, the serial number dates in to 1951. Looks pretty darn nice for 71 years old.
It appears to have been hardly fired. E.g., there's no fouling on the cylinder face, there's only a minor turn line, and the lockup is tight.
I intend to change the hardly been fired thing.