The bottom of the butt (grip frame) . You may need to remove wrap-around grips to see it. Secondary Locations:
The Smith & Wesson Forum is a primary resource where experts help enthusiasts cross-reference their numbers against known production data. smith and wesson revolver serial numbers database
If your revolver has "CHP" (California Highway Patrol) or "NYPD" markings, a database can confirm if the serial number falls within the block shipped to that agency. The bottom of the butt (grip frame)