Just to reiterate. 
WHY? 
We are portraying an Era where these weapons were NEW or NEWish. 
They were expensive, needed to function perfectly, so they'd have been taken rather good care of. 
one of the main reasons is the very inadequate, modern blueing given by the italians to their clones, with no possible comparation to the wonderful rust of heat blueings of XIX century firearms.
so many revolvers, be it Cattlemans, or be it Navies, Armys, 1858, just dont look authentic. In my UBERTI cattleman case, the casehardening was ...

and the blueing was....

..(I dont want to offend Italy´s replica gun industry and their customers, but it is the plain truth...they are light years away in finish from the real guns).
Every time that I saw the gun, I wanted to cry. I just didnt like the finish, XIX century revolvers were not finished with those black alkaline, poorly made finish and with that chemical casehardening, period!
so we have to choices:
either refinish the gun the old way, or either "ageing it".
original heat and rust blueing finishes are more affected by both light and leather than modern finishes, and tend to become "grey", in a few years time, specially if used outdoors. They develop in just 20 years a very nice patina, if exposed to elements or sunlight, and lets not forget that they used not to clean them much, and if they did, they did it with soap and water, that sometimes, if not properly oiled after, will develop rust.
in short, many guns were refinished after only some years of use, by local gunsmiths, and this professionals knew their trade well, so they did refinish them the old way, mainly with rust blueing. So a rust blued UBERTI like mine, will look 1000th times more authentic that an alkaline blued, black, and chemical casehardened one.
the same applies for Pietta, with finishes that really look unrealistic. Well, they are using robots lately to manufacture them....depressing, but very cost effective indeed....
all the best