Walnut stocks were optional on the I frame at that time, so no, not common. You're correct the Gutta Percha hard rubber stocks were standard.
Introduced beginning with the Model 1891 single shot, were factory produced optional Extended, two screw, plain and checkered walnut stocks, and round butt pearl and ivory stocks, later stag as well, and all except walnut, had small round recessed gold plated over brass, S&W medallions inlaid.
Single shot grip frames are the same as I frames, so I have no doubt that not only the extended 2 screw walnut target stocks but also round butt walnut were optional for the .32 I frame. We've seen a few with matching serial #s to the guns they were on. These would not have medallions until 1910.
Stamped since 1857, stock #s, always right side only, changed to penciled #s c. 1900 and back to stamped #s in 1929. Scratched, penciled or stamped on hard rubber and premium stocks; numbering discontinued ~ late 1970s. Pre war penciled S/Ns are in the top half of the stock near the backstrap and read with the stock oriented with the back edge down. Sometimes a photo like this one is needed to “see” the penciled # as shown below:.