It is a .38 Military & Police, after 1957 named the model 10. Depending on if the number 3971 is off the bottom of the grip frame, it appears to be a very early one called the model of 1902. The number inside the frame is an internal factory code and not the SN in a gun of this era.
The barrel probably was stamped ".38 S & W Special & (second line) U.S. Service CTGs", the latter referring to the .38 Long Colt cartridge. .
If this gun could talk, its speech may be slurred and memories not too clear. Hope this is helpful.