As I said earlier, there is more than one way to surface harden parts than true Case Hardening. Watch the video that CraigC posted. You will see the frames being dipped into a hot salt bath and then quenched in water. The narrator of the film makes several mistakes. One of them is calling that process Case Hardening. It is not true Case Hardening done the way I described, although it will raise the surface hardness of the parts somewhat. I guarantee you that you will not get true bone Case Hardening with a gun in the Uberti price range. True Case Hardening is labor intensive, much more complicated than dipping parts into a bath, and it is expensive. If you want true Case Hardening done the old fashioned way, you will have to pay more.
As I said, the narrator of that video makes several errors. For instance guns are not proofed at three times normal operating pressure. More like 1.2 to 1.5 times normal operating pressure. Three times would have destroyed the gun. But the video is very useful for seeing some of the processes that Uberti uses to make their guns, for instance forging the frames from red hot ingots and then final shaping on CNC equipment. The way the wooden grip is shaped with the metal grip parts is also interesting, that is the way it has been done for well over a century.