This appears to be a .38 Single Action model of 1891. It is a fairly uncommon gun and in some ways resembles a down-scaled model 3. Are there any stampings on the top barrel rib?
It has been refinished and the trigger blade does not appear factory. One of the antique experts will be along shortly with more information.
You have a .38 Single Action, 3rd Issue (type) that is commonly called "the Model of '91". The Model of '91 appears on the barrel rib along with the S&W name, address and patent dates, etc.
The revolver is not often encountered even though some 25,000 frames were manufactured. More common are the Single Shot pistols which share the same frame.
As stated above, the gun has been re-nickeled and the trigger geometry indicates that the mechanism has been messed with.
It does appear to have some sort of issue with the trigger, since it is too far forward in the trigger guard but is the correct shape for factory original. The stocks are not original and, as said above, it has been buffed and re-plated. Lastly, the sideplate screw is a replacement.
Properly known as a 38 Single Action, 3rd Model, but many call it a Model 0f '91 since that is what is stamped on the top rib of the barrel. The factory started production of this model in 1891 and your revolver would certainly would have been a first year production. There were 28,107 frames made and some were fitted with single shot barrels. Best guess is that there 1343 single shot and combination guns made. Also, there were about 2000 made with spur triggers for the Mexican market. Lastly, there is an entry in Martin Rywell’s 1953 edition of Smith & Wesson – The Story of the Revolver. where he claims that 7,000 Model of 1891 revolvers were made for the Russian trade. That leaves around 14,000 38 SA 3rd revolvers made. They are uncommon, but not scarce.
Someone made a valiant effort to restore this revolver however although it looks good at first glance, there are glaring examples of the refinish under close inspection. S&W side plates fit so that the seam is virtually gone. In the case of this revolver the seam looks like a separation in the metal. On the butt of the gun there are buffing marks that appear diagonally.
You will need to post a photo of the barrel address and confirm that all the numbers match before the members can confirm it's correct?. Barrel, latch, cylinder numbers must match the frame number you show photo'd. Since the gun has been re-nickeled and heavily buffed? It might be a put together with non matching parts. Very common. Advise caution if you are considering buying. A mismatched gun has a much lower value. Even a rarely seen variation like this one. Falls right under the title: "Parts gun".
The trigger issue is commonly associated with a chipped or worn trigger spur(sear) or hammer notches. Which can be repaired with a good weld. Many are welded!!
Also, re-nickeling of this type "OFTEN" is performed to hide "issues" with the gun. Welds, various repairs, miss matched parts, cracks, bulge repair. Often a de-milled gun that was cut in half then welded back together and refinished. Many possibilities.