There are several indicators that it has been refinished. The trigger gaurd and trigger are nickel coated. The gaurd should be blued and the trigger would be case colored. The edges are rounded and heavily polished. The head of the stud on the right side that the side plate screws into on the left side is flattened. It is very hard to remove (read that as almost impossible) and most refinishers can't remove it, so they just polish it down. It is a 4th model and was made between 1898 and 1907. The distinguishing characteristics of the 4th model are the knurled lift latch on the barrel and the pinned front sight. It looks to me to be pinned and polished down. If it is not a pinned front sight then it is a 5th model. A gun of that age should be checked by a gun smith before firing it the first time. It was designed for black powder but the smokeless rounds sold for it are anemic enough that they should be alright too.
Mark

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Mark Connot