I would high polish and color case the lock and breech (or rather have Keith Kilby at Wyoming Armory do it). Maybe the trigger plate too.
I would perhaps put a weak rust blue (kinda greay blue) or brown on the barrel and then do about a 320 polish on the rest of the steel and heat blue them. If done right this will give a pleasing pale blue that is not very shiny at all.
This will give a good hunting rifle finish.
Then after some use you can determine where to enhance the wear a little if you just gotta have a gun that looks used. Grey all over is not a used gun, its a gun with grey finish. While popular it is generally grossly incorrect for someone thinking he wants a "used gun" look.
Looking at the rifle below it is hard to say how it was finished except I am confidant the lock was hardened.
Considering the remaining finish it could have had heat blue on everything else, or nothing.
Then again we don't know how its been treated in its prior life it could have been "fixed" at sometime and all finish removed from the metal to cure surface rust. The barrel looks too clean, no finish in protected areas. It would require detailed disassembly to get a good handle on this and maybe not then but this is not going to happen. The rifle having links to Jim Bridger.. I doubt it was mirror polished and really doubt it went out in the white. Shiny guns were not popular in the west they can literally be seen for miles if they reflect like too well. I over polished the patch box on the English style sporting rifle and its like a mirror and makes dancing reflected spots on the ground when the sun hits it right. Need to rust blue it after engraving, if I ever get around to it.
Will be back in Helena in January and will try to get by and eyeball it again.