This is evidence that S&W Customer Service people do not necessarily have any knowledge of the old guns. Your revolver is a pre-WWII I Frame. See the mainspring strain screw in the lower end of the front grip strap? The J-frame extractor rod will have left-handed threads. Your gun has right-handed threads.
The progression was from I-Frame with the flat mainspring, to the Improved I-Frame with the coil mainspring, to, eventually, the J-Frame. It is my understanding that in the late 1970s there was a fire at the factory, in the service department. The majority of parts for the older models that were not damaged were sold at that time to David Chicoine,
David R. That is where you need to look.