they are typically selling anywhere between $550 & $750.00 depending on condition and region these days
most that I have seen in local dealers case in my area are asking around 6-675.00
the older Smiths usually sell for more than new ones (better fit/finish and no internal lock) IMO
If you bought that gun brand new in the early Eighties you probably paid approx. 195.00 to 220.00 dollars for it. I have a Model 66 with 6 inch barrel same as yours and I paid 220.00 brand new. It came in the Blue S&W cardboard box with cleaning rod, small screwdriver, bore mop and brush.
A very good all around revolver to be used with 38 specials. A steady diet of 357 mag will stretch that frame (I ruined a model 19 that way).