On my newly acquired 4006 I found a bar code label on the box showing the serial number and that it apparently was originally sold to and then repurchased from the California Highway Patrol by S&W. My question pertains to three matching numbers found on the barrel, slide, and receiver. Were these parts matched at the factory for better accuracy? If so I wonder if that was part of the specifications required by CHP?

The way it was explained to me is that the four digit number is what CHP uses for tracking their guns, for some reason they don't use the serial number.