Of course we do not know what parts may have been replaced during the guns period of use as a Cavalry revolver. If they are the correct parts, with the proper appearance of wear, as collectors we can assume the parts are original. Fair enough I believe. No one can prove otherwise.
Where we have absolute proof that a 130 year old gun has had parts replaced in the past couple of years, that is a different matter than the mere possibility of a gun having had a part replaced during its historic use as a Cavalry revolver.