Stinger63: AHS5xxx is the serial number - it indicates your .357 was manufactured in 1986. For future reference, the definitive serial number on S&W revolvers is stamped on the butt of the gun, i.e., the bottom of the grip frame where you took yours from; it is sometimes necessary to remove the trips to see it. Letters, numbers and symbols stamped onto the side of the frame under the grips usually mean nothing but can at times indicate that the gun was returned to the factory for refinishing and/or mechanical alterations.
There are a number of possible models it could be (I'm guessing Model 19, but who knows) - you'll find the model number, along with the serial number, and likely a few other numbers and/or letters you can ignore, inside the frame cutout - the part of the frame that's exposed when you swing the cylinder out.
The W.R.P.D stamping most likely indicates the gun was once issued by the "W.R." Police Department, but I have no idea what the "W.R." might stand for.