All of S&W's parts have a number that could be used in ordering replacements. Stocks panels were no exception. The right panel has part number 5214 and the left panel 5210. The numbers were not always stamped on the stocks, but many times they were. You also see this on N-frame stocks as many are stamped NT-430 with the corresponding part number and for the Combat Magnum, KT-357, with the part number. The parts sheet shown below is dated January 1, 1957 and you can see the part numbers for the target stock panels (the parts sheet is for the Combat Magnun, KT-357).

Bill