It depends somewhat on: (1) condition, and (2) when it was made. The serial number will date the year of manufacture. In general, collectors like earlier guns in mint to near-mint condition while shooters tend to go for later production - particularly those with checkered walnut grips rather then back hard rubber. This however doesn't make a particular gun shoot any better.
Depending on when it was made, the original magazine will add to the collector's value, but if your looking for a shooter be sure the lips aren't cracked or bent, and you may want to replace the spring.
Be aware that many otherwise good guns have badly pitted bores. Replacement barrels are available, but if a new barrel is needed its cost should be factored into the price of the gun.