Kid,
I'm going to go out on a limb, and guess you really are a kid, or at least younger than 30, or so. Bear with me.
That finish is what is known as cyanide case coloring, a process that came on strong after about WWII. I believe a few American guns had that finish, usually lower end guns like Stevens and Savage shotguns. My Darne was built in 1946, and would have been among the first finished with that method.
It was easier and cheaper than true bone pack case coloring. The "loss leader" of the Darne gun line, post WWII, the R10, was always finished that way.
I'm told that the cyanide process does impart some hardness to steel, but, I've seen plenty of examples with "flaked" finish, and wonder how hard they can be. Post WWII, Darne started using alloy tool steel forgings of higher quality than the pre-WWII Darne guns, so, maybe it doesn't matter what the hardness is. Standard proof Darnes got French TC steel forgings, magnums got XTC, both are molydenum steels, XTC is higher in chrome, and a [censored] to blue, by the way.
I like case colors on a gun, but, will admit I like true, bone pack colors, better.
Best,
Ted
