The easiest way to tell, if you have the gun in your hands, is to look straight down behind the hammer and cock it VERY slowly. You can then see the sliding hammer block (if you have one) move down and out of the way of the hammer. On the plus side, you have a 4" barrel, the gun looks like it has not been abused, and it is chambered for .38 SPL, not .38 S&W like mine, LOL. You can shoot conventional modern ammo. In practice, the hammer block only matters if you are planning to be dropping it on concrete... or a steel ship's deck.