Quoted:
One thing to note is your description does not match your % grading. If there is no bluing wear at all, that means there is 100% original finish on it, and that is what the "%" means. 95% rating means 5% of the bluing is gone and you are looking at bare metal, pitts, or rust. So really it sounds like 99% with some handling marks. The trigger and hammer should have vibrant case-hardening in a condition to match the finish, too.
Did you do a check-out on the mechanicals? There are stickies in most gun forums by Jim March on that proceedure. That will let you know how it is mechanically.
Next pricing point is the grips - are they original? If they are '68 or earlier, they should be walnut "magna" style grips with elegant diamonds around the screw holes on either side. Either way, removing them and looking inside the right panel should show the s/n of the gun stamped into the wood. If that's the case, then anything around $400 you can negotiate is a good price. Beaters are doing $300 these days (and what dark days these are ;)).
If they are missing the original grips, you should negotiate $50 off the price right there unless they have some rarer, fancier factory grips on them like smooth targets or Combats or something.
The marks I was looking at are some little "nicks" for lack of a better term on the underside of the barrel and one on the back strap of the grip. They look like something rubbed or hit in the spots, not the steady wear of a holster on edges. More like marks from knocking around in a drawer/nightstand, didn't look like any type of pitting/rust. There is very little cylinder drag in the bluing where the cylinder rotates at the lock notches. Lock up when cocked single action was very tight. Action had a nice solid feeling and "clicks". Grips appeared to be original, no dings or rough spots. If I recalled the serial number correctly it was K78000X. I don't recall a number in front of the K (I have a nickel model-15 already that starts with 3KXXXXXX and dates to 1971). Gun was a Model 15-2. I only gave the percent indication, meaning the gun isn't new and has some marks on it, it's hardly been abused from the way it looks (I'm not that up on gradeing stuff beyond my own scale).
Low end on a nice one is $400. $450 more typical. Very nice ones can run $550 and up. They are very nice pistols. I've been in the market for one of these ever since I got the 22 lr equivalent in a Model 18. A Model 15 also makes a very good self defense revolver with all of the good .38 special rounds being produced for CCW models.
I went to the police academy back in 1987 carrying a Model-67. I regret selling that gun and I have been running across model-15's lately. It's essentially the same gun. When I was a kid, I pleaded with my dad to buy me the Model-18, I recall seeing it at the local Montgomery-Ward's in the sporting goods area. I think it was $175(circa 1980, I think). Now they are tough to find for less than $550.
If I can get back to the gun store one day this week before they close (store hours are 9-4, and I work til 5 with a 45 minute commute home), I want to look at it again, and decide if I'm going to buy. They are open on Saturday, but I'll be out of town this weekend starting Thursday night.