Just bought my first S&W model 10 today! .... The serial number is 357xx.
Where are you finding this number? If it's inside the yoke cut under the model number, it's an assembly number, and you need to read the serial number off the butt- refer earlier in this thread.
If you're reading this number off the butt, it's a .38 Military & Police Model of 1902, 1st Change, manufactured in 1903 or 1904. If it's really this old, you must post some pictures.