J-Bar your Model 686 Distinguished Combat Magnum was manufactured in 1984. Guns in the AEVxxxx to AFJxxxx range shipped in November of that year.
UNless there is an M stamped near the serial number, it is subject to a recall. With some magnum ammo there is the chance that the primer will flow back around the firing pin, locking up the gun. Under the recall S&W will pay shipping both ways and install a new pin and bushing. The M stands for modified, and is proof the gun has been fixed.
NottheFace:
Your Model 1917 .45 Hand Ejector U.S. Army falls into the very tail end of the US Army serial range of 1-1695959, so the frame was probably produced in December 1918 or January 1919.
It almost certainly shipped in 1938, there was a large shipment of guns in the serial range 181983 to 207043 that year, I assume (yeah, I know) S&W would have used up old stock before beginning production again. The gun predates the introduction of the non positive hammer block safety. Wether it was retrofitted to your I don't know. Regardless, it was replaced with a positive hammer block after a fatality with a dropped gun in WWII. I would treat this gun as a five shooter, if kept loaded leave the hammer down on an empty chamber.