Hello I have a model 1860 serial number 104835, it appears to be a civilian model as it has 3 screws on the left of the reciever there is no scene on the cylinder and the gun appears to be nickel as there is no bluing any ideas .
Every Colt with an unfluted cylinder had a scene. This scene was there to prove that the gun was a real Colt and not a copy. So, if yours does not have a scene, it's either because it is worn away or because it's not a real Colt.
Nickel was the new fangled finish in the 1870s and later, and it was easy to have a gun, or any metal object, plated at the local hardware store to make it look better than new well into the early 1900s. You couldn't get a gun reblued locally, but many hardware stores had plating tanks (they didn't have to worry much about disposing of the toxic chemical mix used, unlike today).
So, many an old veteran of the Civil War was polished and plated.
That's what happened to yours.