JEW-III.
If the gun is a top break, with exposed hammer, then it is a .38 Double Action 2nd Model, manufactured between 1880 & 1884. This is a black powder only proposition and should be treated as a 4 shooter, with the chamber under the hammer left empty.
If the gun is a top break with enclosed hammer, then it is a .38 Safety Hammerless 3rd Model manufactured between 1890 & 1894. This is also a black powder model, but should be safe to carry with all chambers loaded.
If the gun has a swing out cylinder and 5 chambers, then it is a .38 Regulation Police (4 inch barrel) or .38/32 Terrier (two inch barrel). These are post war guns, if there is no model number stamped under the cylinder yoke then they fall in the period 1948-1957.
If it has a leaf mainspring (there will be a tension screw in the front strap of the grip) then 1948-1953.
If a coil mainspring (no tension screw) then 1953-1957.
If there is a screw holding the side plate in front of the hammer, then 1955 or earlier.
If no screw, then 1955-1957.
With the above you can narrow its age down to within a couple of years. Postwar guns have a positive hammer block safety and can be carried fully loaded. They are suitable for use with modern ammunition.