Date is likely 1920-21. I am assuming that the S is spurious, and the number is 370100. If it is something else, please correct. It should not have the "Made in USA" stamping on the frame as that came later, and the original grip panels would be checkered wood with center diamond and no S&W medallion. It is correctly called the Model of 1905, Hand Ejector, Military and Police, 4th Change. Surprisingly, many of these M&Ps from the roaring 20s survived in excellent condition. They are my favorites. A picture would be good.