metzgarj:
Gun 4, assuming a top break action and enclosed hammer, is a .38 Safety Hammerless 5th Model manufactured between 1907 & 1940 in the serial range 220000 to 261493. For the decade up to 1907 the 4th Model was produced at a rate of roughly 10,000 a year. If I had to guess I would place your gun somewhere between 1907 & 1917. In 1907 Colt released its swing out cylinder Pocket Positive/Police positive and in 1917 S&W began production of the swing out cylinder .38 Regulation Police in the same caliber began. After that demand for the old top breaks would have died.
It should be fine with modern factory ammo, S&W started advertising their guns as safe for smokeless powder sometime between 1906 & 1909. It lacks a hammer block safety and could fire if dropped. Leave the chamber under the hammer empty.
Gun 3 Serial number 51746, assuming a top break with exposed hammer, is a .38 Double Action 2nd Model manufactured between 1880 & 1884 in the serial range 4001 to 119000.
If a top break hammerless, then it is a .38 Safety Hammerless 3rd Model produced between 1890 & 1898 in the serial range 42484 to 116002.
Either way this is a black powder gun, don't shoot modern smokeless ammo through it.
The pinholes are not a factory item. If they are through the rib I don't see an issue with them. If they penetrate the barrel consider it unsafe to shoot.
Gun 2 serial number 131750 is potentially a Model Number One 3rd issue. These were manufactured in a serial range 1 to 131163 between 1868 & 1881. As your gun falls outside of that range it may be a counterfeit, or it may be production ran a little longer than researchers think. In which case it is almost certainly an 1881 gun. Value in excellent condition is around $600, as new $2500, the original case may be worth up to $6000 if present. Do not shoot this gun. It was manufactured for use with a black powder .22 short cartridge, not modern smokeless ammo.
Gun 1, if it has a square butt is a .32 Regulation Police, if a round butt a .32 Hand ejector 3rd Model. Either way it was manufactured sometime between 1929 & 1940.
This gun is fine with any factory .32 S&W Long ammo. Be aware that it lacks the modern internal hammerblock safety. If dropped it could fire, so leave the chamber under the hammer empty.