Serial numbers for the 4th change 1905 started at around 240,000. The SCSW reports that cylinders were heat treated on these at around serial # 316648. I'm wondering if this would make the date of manufacture of yours at just after the end of WWI, when S&W regained control of production from the government. Someone else will surely chime in with more specific details. I think the "made in USA" started at this time period too. The non medallion stocks are consistent with 1920's too. Nice find at a great price! I would think that you could easily double your investment if you cared to!