The Model 19 you are describing is a Performance Center gun. I owned one for a bit. The pluses are that it has the smooth action job that the S&W Performance Center does on their guns; it is a 3" barreled K-frame with the excellent "hang" or feel that the 3" has (along with a full-length ejector rod); It has a night sight, the port is a single, large port in front of the front sight, and it does work to reduce muzzle jump. Mine had chamfered charge holes. It is just about the ultimate in a combat revolver.
There is a downside to the gun: The matte blue finish is prone to rust faster than a polished finish. You have to look farther than the corner hardware store for a proper holster, but they are readily available from folks like Desantis. Although the barrel is 3 inches long, the sight radius is about like that of a 2 1/2 inch gun because the front sight is set back to allow for the port. That is not a factor at combat ranges, but I could shoot better groups with a standard 3" K-frame at 25 yards than with my PC 19.
If the gun is in solid condition, not worn to a sloppy frazzle, it is probably worth 500-550. A reblue is not exceedingly expensive. I don't think I would go the $700, but a compromize price might send it home with me.
Clemson