It's an excellent price on a 686.
Check to see if there is an "M" stamped on the inside of the crane area next to the model number.
The 686 (no dash) and the 686-1 had a recall on those models due to the cylinder binding on soft primer material; the primer would flow into the firing pin hole on firing and cause the gun to lock up. S&W replaced the firing pin, AKA the Hammer nose, and the firing pin bushing in the frame.
I just noticed the post before me actually gave you a link to this problem.
In any case, it's a great looking gun at a rarely seen price.