When an FFL obtains a firearm with more than one serial number, then both serial numbers should be recorded in the A&D book.
One serial number may be the importers serial number and the other number may be the manufacturer's serial number. If a gun trace starts it will be with the importer, so use that serial number first with the other serial in parenthesis.
example: XYZ123 (104-6535)
Note: FastBound will give you a warning telling you that you've entered invalid characters. That is because the parentheses are invalid characters to be used in a serial number. But, in this case, you need them to separate the two serials so continue and ignore the warning.