An exact DOB will require a factory letter.
A range would be:
1) S&W New Departure in .38 S&W, s/n 185120 -
This would be a 4th Model made 1898-1907, serial range 116003-220000
2) S&W Model of 1905 M&P in .38 spl with a 6" barrel, s/n 227169
This would be a 3rd Change made 1909-1915, serial range 146900-241703
Dean