As Alan says, the .38 Military & Police is the important identifier.
It is also important to note (and offering this for sale where knowledgeable people would see it, this matters), that the serial places it very close to the beginning of war production, likely in 1940 or shortly before. We see very few standard civilian editions in .38 Special from that time any more; somewhat lower than your gun, around 670,000, S&W had started shifting to large-scale production of the British Service version.
Combined with its very good and apparently all-original condition (check inside the right grip panel for a matching serial number), that should make this gun a bit more interesting to collectors than one from a few years earlier or a post-war specimen.