You have only provided a generic description. Trying to put a value on anything with just this limited information provided is difficult. Value depends on a combination of many factors. Without a detailed description to include, finish, barrel length, overall condition, stock material, sights, box, original paperwork and any accessories, only a general estimate can be given. This weapon could be in the 100-1000 USD price range.
1948. Worth spending the $30 to get it lettered by Smith and Wesson, IMHO.
1948
Look on the butt of the revolver.
@1947
100-1000 USD.
i think 1966
Standard Catalog of Smith and Wesson, 3rd, ed.
Less than 100 to over 1000 depending on specifics.
100-400 or so
Call S&W with the serial number or look it up in the Standard Catalog of Smith and Wesson, 3rd ed by Supica and Nahas.
If you call S&W, they will tell you.
Your Smith and Wesson K-22 was made in the year 1948,with the serial number K20708.That year the serial numbers were K18732-K73121.I hope that you find this informative.