I would guess 1941 or 1942. This was marketed as the Military & Police.
Note that this revolver is chambered for the .38 Smith & Wesson cartridge -- NOT the much more common .38 Special. Many revolvers from this era were converted to shoot .38 Special and many of those were converted VERY crudely.
The proper .38 S&W ammunition is much more difficult to find (you can order it online but most stores don't carry it) and it will cost more money than you may expect.
The pearl or faux-pearl stocks are not original. This revolver also has the older style "long action." The 40916 number is an inside assembly number that was used during manufacture and has no relevance now.
I am curious about the "p" suffix you see at the end of the serial number, that's not something I'm familiar with and it is not shown in your pictures.
I am -no- authority on this but I believe the "poorly converted" gun simply had the chamber reamed for length... the net result is a revolver that is basically safe (mostly safe...?) for shooting .38 Special however accuracy can be less than optimal as the bullet diameter of .38 Special is undersized. The bigger issue is that .38 Special brass swells in the slightly larger diameter chambers and the brass can or will get wrecked.
All of this is moot if your revolver is original and not altered.