You have to go by the serial number 29-2's were made into the 70's i believe, as mineare -2's and i bought them back then.
Every little detail makes a difference in the price. Here's some of them...What is the condition of the wood box? Are all of the access.. with it? Are the access..the right ones for "that" gun? Condition of gun? do you have the origional paper work? do you have the box the wood box came in? The type of grips and kind of checkering they have on them?
It's collectable, and every detail makes a difference.... As for mine, they are hunting guns and i don't give a damn what they are worth... When i'm takeing my "eternal dirt nap" somene else can worry about that...
For the last word on S&W's there's no better place than here
http://smith-wessonforum.com/eve They know every detail to every S&W made! On top of that, they are a great bunch of guys...
DM