For the purposes of legal action that might be taken against a purchaser, it is the number of guns that are reported stolen and available to be found on a database searched by police that is important. Many millions of guns were manufactured before the government started to mandate that guns have serial numbers. There is no way to determine if those firearms were stolen, unless there is some sort of distinctive marking that could connect the firearm to a previous owner. That sort of marking could be input into the FBI data base nearly as easily as a serial number.
The FBI has maintained the database of stolen guns for the United States since 1967, so we have about 46 years of data in the system. There are a few state data bases, such as Florida’s, but it is a reasonable assumption that most of the firearms in state databases would also be reported to the FBI for inclusion in the National Crime Information Center (NCIC) system.
FK – We need to repeal GCA ’68 and the NFA. Stolen weapons could be dealt with via a public but privately owned internet database with serial numbers only being recorded by the companies that make the weapons and those who purchase them, as it should be.