Do you know the year or "dash number"? For example:
686 no dash, 1980 introduced model
686-1, 1986, radius stud package, floating hand
686-2, 1987, changed hammer nose, bushing and associated parts
686-3, 1988, new yoke retention system
686-4, 1993, change rear sight leaf, drill and tap frame, change extractor, hogue grips
686-5, 1997, change frame design to eliminate cylinder stop stud, eliminate serrated tangs, change to MIM hammer with floating firing pin, change to MIM trigger, change internal lockwork
686-6, 2001, internal lock
I have an early one with 6 inch barrel I bought about 1983. I see nice examples of those down here in the SW in the $650-750 range in very nice condition with the box. Not new in box but not scratched up much either.