I think any revolver with at best 75% finish, pitting at the muzzle and that the seller drops 20% their asking price on, needs especially close mechanical and visual assessment.
I'd be concerned about pitting all the way down the bore. If it's minor "salt-and-pepper" it won't harm function but should bring the price down. I'd look closely at each chamber to make sure there's no pitting in there; pitting in a chamber can affect case expansion under fire and cause empties to stick during ejection -- unacceptable if a defense weapon.
I'd measure barrel-cylinder gap, headspace, endshake, uptake on each chamber in single and double action, and so on.
Sometimes a seriously cosmetically challenged revolver is only that, has great mechanicals and is a good deal as a shooter; sometimes, though, a cosmetically unloved revolver signifies a mechanically unloved one, too. And if there's anything mechanically in question, you have to pay to have that fixed and then the deal isn't such a good one unless you spotted the problem before purchase and used it to further drive the asking price down.
Often it's easier to pay a little more up front for a revolver in all-around good shape.
Here's a good link about assessing used revolvers for purchase:
https://docs.google.com/file/d/0B6F...hLWE4YzMtOTdmN2YwNmY4NzM2/edit?hl=en_US&pli=1
All told, if the Model 19 in question checks out with flying colors on everything but the issues you already mentioned, $400 is about right in the current market. I'd still push for less.
The 3" Model 13-3 is a significantly more compelling purchase in this case, I think. $500 for the revolver alone isn't bad if it's in NRA Modern Gun Condition Standards "very good" or better:
The National Firearms Museum: Evaluating Firearms Condition
The short barreled Model 13s are all-around outstanding revolvers for a variety of uses and are being hunted to extinction. I'd snag that now for $500 easy if it checks out mechanically and pick up a better 19 later.
Welcome to the forum.
