A Smith & Wesson Model 15, similar to the one used by Al Powell.
The Model 15 is a revolver created by the Smith & Wesson firearm industry. They were produced from 1949-1999. The Model 15 holds .38 Special and can fire six rounds. It only appears in Die Hard and was Al Powell's service pistol while with the LAPD.
Die Hard
Disguising himself as one of the hostages, Karl emerges from a sheet covering his Steyr AUG with him, and attempts to kill John McClane one last time. But before he can fire at him, Sergeant Powell of the LAPD draws his gun quickly, and shoots Karl multiple times with it, eventually killing him and saving the lives of McClane and his wife Holly Gennero.