Berdan - you sure made me do a "double take" when I saw the picture of it. Believe it or not, I recently sold an original piece that is identical to that with the exception of the lock marking. I had purchased it at an auction probably close to 50 years ago. I even sent a photo of mine to Robert Abels - he was a well known dealer in NY many years ago and he put out catalogs of antique firearms that he had for sale on a regular basis in the 1960s). Based on the markings on my lock (unfortunately, I don't remember exactly what they were and I don't have access to them as I'm in AZ for the winter) he figured that what I had was a "French Coach Pistol". Basically, a small pistol carried by passengers for protection at the time. Mine had a bore that appeared to be about a .69 to a .75.
What you show in the photo looks like a very nice repro. I'm sure it would be fun to shoot - not terribly accurate though unless for up close SD distances.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63