I have never seen or heard of a factory case hardened Ruger semi-auto. The only thing I have seen it on are Ruger single action revolvers. Even if Ruger did do some semi-autos it is not case hardening as shown in Skeet Mans photo. Ruger used a chemical "case coloring" process. I don't know what that is on your .22.
Yea I seen the Turnbull was doing some on the new Mk IV's. Not my gun. Was considering buying it, marked "Target" but only 4" barrel. Just never seen anything like it. Hard to tell if there is a clear coat over it.
I have many Rugers, in my opinion the factory bluing is probably the least protective of the major manufacturers.
My 6" like the one pictured, has a thumb print, rust mark, from accidentally touching it after cleaning it for storage.
I would guess the one in question, was probably used and not taken care off ,then an attempt to make it look better.
I had a customer whose Ruger looked like that. It wasn't looked after very well, never cleaned properly or oiled, and started to rust, so he tried 0000 steel wool to remove the rust. It removed the rust AND all the bluing eventually, leaving a pretty shiny barrel. He didn't learn from that experience and the barrel rusted again. He eventually got tired of scrubbing it and oiled it, but the damage was done and it ended up looking like the barrel shown above.
We must have had a sale on "Rugers for Dummies". I had a customer phone in complaining that the "inside of the barrel was coming apart." I couldn't figure out from his description of the problem just exactly what was wrong, so I told him to bring it in for a looksee. It turned out that he ran a bore snake through the barrel once after shooting it and figured that was cleaning it. The grooves eventually filled up completely with lead, and what he figured was the inside of the barrel coming apart was actually lead shavings being forced forward out of the grooves. We got a .22 brush on a rod, put down a sheet of typing paper on the counter, and rammed the brush through the barrel while the end was over the paper. He was surprised to see the inside of his barrel coming out onto the paper and was immediately talking replacement pistol, complaining directly to Ruger, etc. We eventually got him to calm down and continued to scrub the lead out of the barrel. It even surprised us behind the counter how much lead came out onto the paper before we decided it was clean. When we showed him what the barrel looked like after a good scrubbing, he was just absolutely amazed, as he thought the lands had been worn out by shooting it so much, and that's why he eventually couldn't see any rifling. We sold him a cleaning kit and reminded him that it needed to be cleaned properly EVERY TIME he shot it, and lightly oiled inside and out when finished cleaning, and sent him on his way, never to darken our counter again.
Gunkote your Ruger with gun metal blue, do your part and it is a beautiful, rust proof finish. Many a shooter at Koko head pistol range could not believe that they were not the same finish, thinking I sent the Ruger to the Colt factory to be refinished, as they were unable to tell the difference between my mint 76' Colt Mk IV Series 70 Gold Cup in Colt Royal Blue and my Gun-Koted Ruger MK2. I had a lot of request to refinish people's pistols almost every time I brought them both to the range.