I would look for a older model 27 with a 3.5 inch barrel. They are not common and will cost you around $700.
Good luck,
Howard
You cannot go wrong with this. I wish I had the box and papers though.
27-2, 3.5" barrel
5" Model 27's are nice too.
Condition however is everything. At least for me, they don't have to be unfired. I'm going to shoot them anyway, at least a few times. You can use a gun, but you don't have to drag it behind a truck.
Model 29-2, 44 Magnum, 4" barrel.
Nice grips, especially factory grips can make or break a gun. Target hammers and target triggers are nice too. At least I think so. Others don't agree.
Don't overlook all of the newer guns though. While it might not be a "collector" gun yet, it is a very nice gun made in limited quanities, and will become one one day. Even if it doesn't, it's a fun gun to have and to shoot.
Model 21-4, "Thunder Ranch" edition, in 44 Special.
(Yes, it does have "the lock.")
If you think all the information you've gotten here is confusing, pick up a copy of the "Standard Catalog of Smith & Wesson." It's a mind boggling encyclopedia of Smith & Wesson with more information than you can shake a stick at.