Howdy
When speaking about S&W Top Break revolvers, it is typical to refer to the largest of these, those built on the #3 size frame, as #3 revolvers. There were five distinct models built on the #3 size frame; the American Model, the Russian Model, the Schofield Model, the New Model Number Three, and the 44 Double Action. It is not as common to refer to the smaller Top Breaks by frame size. Yes, they can be called #2 or #1 1/2, but they are more often simply referred to as 38 Double Action, 38 Single Action, 32 Double Action, 32 Single Action, etc.
This is a 44 Double Action, built on the large #3 size frame. ALWAYS six chambers. Most commonly chambered for 44 Russian. Less commonly chambered for 44-40 and much less commonly chambered for 38-40. Note the vertical grooves on the cylinder. This model ALWAYS had vertical grooves on the cylinder. This is a big gun, the cylinders were 1 7/16" long on the early ones, 1 9/16" long on the later ones. The last patent date on this one is May 11 & 25 1880. This one is chambered for 44 Russian, the SN is 24XX and it left the factory in October of 1881. No, that is not the original front sight.
This is a nickle plated target version of the 44 Double Action. 44 Russian caliber, SN 283XX, this one left the factory in August of 1895. The same patent dates.
This is a 38 Double Action, built on the #2 size frame. Looked at by itself, these look very similar to the 44 Double Action, mostly because of the trigger guard shape. However, only FIVE chambers. Chambered for 38 S&W. Vertical grooves may or may not be present on the cylinder depending on when it was made. The earlier ones had the vertical grooves, the later ones such as this 4th Model had a different cylinder lock up system and lacked the vertical grooves. This one is SN 3573XXand it shipped in 1898. However the last patent date on this one is April 9, 1889. That is because the smaller Top Breaks did not come along until after most of the larger ones.
Here is the money shot. Comparing the big 44 Double Action to a 38 Double Action in the same photo. Notice the cylinder flutes. Notice how on the big gun, the flutes are evenly spaced. Because there are six chambers. Notice how on the smaller gun, the middle flute does not appear to be in the center of the cylinder, because there are only five chambers.
But there is a wrinkle. You really need to know how many chambers, and exactly what cartridge the gun was chambered for. I suspect you are looking at a standard 44 Double Action, chambered for 44 Russian. Look inside the chambers. The 44 Russian was a short, straight walled cartridge. There was no necked down area as there is in a 44-40 or 38-40. Just one ridge that separates the cartridge case diameter from the narrower chamber throat. The 44-40 and 38-40 are both bottleneck cartridges, so there will be a funnel shaped section in the chamber before the chamber throat. Also, 44-40 and 38-40 cylinders MUST be 1 9/16" long. If the cylinder is only 1 7/16" long it cannot be a 38-40 or 44-40. Then it is most likely a 44 Russian. Of course towards the end of production S&W was using 1 9/16" long cylinders for all three cartridges, just to confuse collectors.
Here is what the SIX chambers in a 44 Double Action chambered for 44-40 look like. Notice how big the holes are and how little metal is between them.
The reason I mention this is because, officially, the 44 Double Action was only chambered for 44 Russian, 44-40, and 38-40. However, according to the Standard Catalog of Smith and Wesson, a very few, perhaps 10, were chambered for 38 S&W. Obviously, the SIX chamber holes would have been considerably smaller than a 44. Don't get your hopes up, I really doubt Brother in Law's friend's dad found an extremely rare revolver abandoned in an old hunting cabin. Reportedly a few were also chambered for 38 Colt, and perhaps a few for the old 38-44 S&W gallery round, which is not the same as the extra powerful 38 Special ammo that was fired in the 38-44 Hand Ejectors. The 38-44 Gallery round looked like an extra long 38 S&W.
Most likely it is a run of the mill 44 Double Action chambered for 44 Russian. No, S&W did not make it easy, they did not mark the cartridge the gun was chambered for on the gun.
Measure how long the cylinder is, look for vertical grooves on the cylinder, and count the chambers. And get some 38 S&W ammo (not 38 Special) and see if they fit or if they roll around in the chambers.
No, I'm not going to go out on a limb and estimate the value of a rusty old revolver, the size and caliber or which are unknown.
P.S. I guess I should have mentioned the 44 Double Action Wesson Favorite too. Only about 1000 made, with a lengthwise weight reducing groove on the frame above the trigger guard, and a groove down the middle of the top of the barrel rib. Again, I doubt it is one of the rarer guns.
P.P.S. The photo you posted of a revolver broken open is a New Model Number Three.
Like this:
Again, Model 3 does not describe a specific model of S&W revolver, it only defines the size.