As I recall, only about 2000 27-2 4 inch models were produced making it the rarest of the m27 barrel lengths. I'm sure there's a thread on here about the rarity of that version.
You did great picking up that beauty. I have one and it's my favorite N Frame.
I wouldn't hesitate to pay $650 for one- that's a deal these days. They are only going up in value. This one recently had a winning bid of $1425 but has since been relisted and it's already up to $762 with 8 days left. Smith & Wesson Model 19-3, 2.5 Barrel, Nickel Mint : Revolvers at...
For me it would have to the model 39. Great gun to shoot and the grip is the best of any autoloader I've ever held. 3913 and 6906 would be next in line.
They stopped making that model in blued carbon steel, unfortunately. It's now a stainless frame and slide with a melonite finish. I personally prefer the blued steel and I am currently looking for a used one.