We've discussed this in the past up in the older revolvers section. In 1940 S&W produced the K22 2nd model with the modern micro click sight. From what we can figure out, those guns came with the knurled nickel handle. Then after the end of WWII the first guns out with adjustable sights were again the K22 Masterpiece. This time the postwar model. Those too seem to have started out with the same nickle plated sight adjusting tool. Some time in the late 1940s S&W began supplying the identical item except with a blue or "black oxide" coating on the handle. Those continued until the mid 1950s when a very similar item was produced with aluminum knurled handle. Those are easy to tell.
If the OP here has a nickel plated one, its probably worth between $75 and $100. Less if used and the tip scratched.
You can find all this information in Supica and Naha's excellent book, The Standard Catalog of Smith & Wesson. Its the bible on such things. Many of our posters here have contributed to it in the earlier editions. Rumor has it there's another, the 4th edition being discussed. Buy the 3rd now, but then consider the new one in a year or two if it becomes a reality.