The local market has a lot to do with pricing in my experience. Things I can safely say about the one you're offering:
--stainless makes it more "valuable" than blued
--six inch barrel makes it less "valuable" than four inch
--regardless of what fans and enthusiasts believe, it's less "valuable" than a GP-100 or similar Smith & Wesson or Colt revolver
--it's more "valuable" than a similar Taurus revolver
I will also tell you that if I saw this revolver and I liked what I saw with regard to fit, function and no red flags (regardless of external wear, dings and visible use), I would happily pay $400 for this revolver. I prefer longer barrels than most buyers seem to want, and I happen to be looking to add a Security, Speed or Service Six to my cache. I would accept blued for the right price, but I would prefer stainless. Same thing for barrel length... I'd take a four, but I'd rather have a six.
My knee jerk reaction to your question with no actual looking at the gun to pick apart all the details that might drop the "value" is that you are probably about $50 low in price, especially if you intend to bend a bit in negotiation.
If you had said $500, I would suggest that your price is high. But all of this is without actually seeing the revolver. It's
amazing the small details that you can point out when you have some time and good lighting to go over it closely.