This is an interesting S&W Model One, Second Issue Revolver with a very low serial number in the 12,300 range. This would most likely date its manufacture to the early part of the year 1860 when the last of the 1st Issue revolvers were discontinued in the 11,600 range. It's a standard Second Issue with slab-sided frame, one piece hammer, and large oval sideplate. First Model S&W's, both 1st and 2nd Issues, were very popular with soldiers during the Civil War. As America's first cartridge revolver, the small copper-cased .22 cartridges these revolvers used were waterproof and made reloading very easy. The main thing they lacked was firepower but that didn't seem to stop thousands of soldiers from privately purchasing them as a "backup" weapon.
What's unusual about it is the full nickel finish. Originally, these were offered with silver plated frames that came with blued barrels and cylinders. Occasionally, you'll see one with full silver plating. Here is one of our older ads demonstrating these two style of finish:
Nickel finish was not widely available until the late 1860's to early 1870's when it really became almost the universal standard on the majority of pocket revolvers. So how did a S&W No. 1, 2nd Issue made in 1860 end up with a nickel plated finish? Our best guess is that following the Civil War, this revolver ended up being traded in or sold to a large dealer. Rather than sell the gun with its original blued/silver finish which was worn, the dealer sent it out to be nickel plated to increase its value. This was also done to surplus military guns like US-marked Smith and Wesson Schofield revolvers and Colt Single Action Revolvers. Some dealers like Folsom in NY even did their own "in-house" plating. Over the years, we've seen a few of these guns with full nickel plated finishes while others have their original silver plated frames with just the barrels nickel plated. See photo of ad taken from the 1873 edition of Great Western Gun Works in Pittsburgh, PA. stating "full nickle silver plating" for the No. 1, 2nd Issue. If the gun was in good shape, the nickel could be applied directly over a blued, case colored, or even silver plated finish. That appears to be the case here as the markings, corners, and edges are crisp. The metal was not buffed. See photo of barrel address. Also, if you look closely at the frame, you'll see the original silver in places where the nickel has flaked. I think that a dealer, most likely one in the Northeast, got a nice Civil War era No. 2 S&W which had a little bit of wear and just plated over the original finish.
Overall Condition is Fine Condition with 92% original 1870's era nickel on the barrel, 95% on the frame, and 25% remaining on the cylinder. Balance of cylinder has flaked and turned to a dark brown patina with some light pitting most likely formed from black powder residue. All matching assembly numbers and grips numbered to the serial number. Nice working action. Original rosewood grips retain 70% original varnish. Bore is Fair+ to Good with decent rifling. An interesting and very early 2nd Issue S&W that saw most likely saw Civil War followed by post war usage.