Wesson Revolver

How would I determine the year of a Smith & Wesson revolver?

Is there a key to the date codes listed underneath the serial number?

The Blue Book of Firearms Values lists manufacturing years by serial number range groups.
Any good gun dealer should have a copy on hand, or one can purchase a personal copy from one of several on-line dealers such as MidwayUSAcom or CheaperthanDirt.com.

Smith & Wesson LadySmith Revolver