That looks to be a very nice collectible rifle.
When you get a chance, maybe take a photo of the top of the bolt showing the from the chamber to the hammer checkering and maybe one of the bolt face.
Uncommon for one from the B.P. era to have that finish wear and show no signs of pitting around the breech from either powder or primers or any wood shrinkage.
The front sight appears to be a correct Rocky Mountain that was either repaired or modified to suit the owner.
I would be tempted to pull the gun apart to see if the action, hammer, and lever showed any indication of having been case colored. Maybe it is the lighting, but the gun, especially the for-end cap, has that look to me.
Let's hear back with what the LGS says after a look.