Section 11A. For the purposes of this section and sections eleven B, eleven C and eleven D, the following words shall have the following meanings:—
''Firearm'', a firearm as defined in section one hundred and twenty-one of chapter one hundred and forty, or a rifle or shotgun.
''Serial number'', the number stamped or placed upon a firearm by the manufacturer in the original process of manufacture.
''Identification number'', the number stamped or placed upon a firearm by the colonel of the state police under authority of section eleven D.