What's the purpose of the one spent, or fired, case (inside the box, in a little, yellow, sealed manila envelope, signed by an employee and with the particular firearm's info) that comes with new S&W pistols?

Is this some sort of state-specific or federal requirement for new handguns, a fingerprint of sorts, to help match spent cases to a particular gun in the event of an incident where spent cases are left behind at the scene of the crime?