If my understanding is correct, this little jewel would have been made sometime between 1887 (when the "peanut" wood handles were introduced) and 1912 (when S&W discontinued their reloading tools.
Casts four .38-cal. round balls (0.360" dia.), for use in gallery loadings of S&W's blackpowder .38-44 cartridge, as chambered in New Model No.3 Target revolvers. My library is not the most extensive, but the only other example I can find is one for .32-44 on page 218 of "Smith & Wesson, 1857 - 1945" by Neal & Jinks.
Evidently these things are not a commonly encountered item.
Jim