The serial number is stamped on the butt, and probably has a "S" or "C" prefix. It would help greatly if this gun's owner had posted it (using xx for the last two numbers). As it is I have to look for certain features it has or doesn't have to get an idea when it was made. Follow along:
It has a "short action" - identified by the hammer's shape. Introduced in 1948 at or about serial #S 991084.
"S" serial numbers end at #S 999,999 and new "C" serial numbers start at C 1 in 1948
Front sight shape changed from half-round to ramp style in 1952
Upper sideplate screw dropped in 1955
Became model 10 in 1957
Diamond around stock screw deleated in 1968.
So Detective Fuff
would say that this is a pre-model 10, postwar Military & Police .38 Special revolver, manufactured sometime between 1948 and 1952. The stocks however are "incorrect for period," replacements, but still made by Smith & Wesson. It appears to be in pretty good shape, has a scarce (but not rare) 5" barrel, and is probably worth around $300.00.
So can you do this at home? Sure! Just buy a copy of
Standard Catalog of Smith & Wesson / 3rd. edition; and you'll be just as smart as I am... Or almost so.