After WWII, S&W used an prefix on all N-frames. This indicated the new hammer block safety. The S prefix is the most common marking on classic post-war N-frames.
A Smith & Wesson N-frame is more than a tool; it’s a historical document. The serial number is the spine of that document. An "S" prefix tells the story of a post-war America hungry for power. An "N" prefix in the 800,000 range whispers of the last days of hand-fitted revolvers in the 1970s. A three-letter prefix like "CAB" marks the transition to modern CNC machining. smith and wesson serial numbers n frame