; (ii) the offer to sell, sale, or transfer of a firearm to, or purchase or receipt of a firearm by, a licensed manufacturer or importer before January 1, 2020; or (iii) transactions between licensed manufacturers and importers on any date. (bb) It shall be unlawful for a person other than a licensed manufacturer or importer to engrave or cast a serial number on a firearm in or affecting interstate or foreign commerce. (cc) Beginning on January 1, 2020, it shall be unlawful for any person other than a licensed manufacturer or importer to possess a ghost gun in or affecting interstate or foreign commerce with the intent to sell or transfer the ghost gun with or without further manufacturing or to manufacture a firearm with the ghost gun. . (c) Requirements Section 923(i) of title 18, United States Code, is amended by adding at the end the following: The serial number shall be engraved or cast in metal or metal alloy and sufficient to identify the firearm and the manufacturer or importer that put the serial number on the firearm. . (d) Penalties Section 924 of title 18, United States Code, is amended— (1) in subsection (a)(1)(B), by striking or (q) and inserting (q), (aa), (bb), or (cc) ; and (2) in subsection (d)(1), by striking or (k) and inserting (k), (aa), (bb), or (cc) . 3. Modernization of the prohibition on un­de­tect­able firearms Section 922(p) of title 18, United States Code, is amended— (1) in the matter preceding paragraph (1), by striking any firearm ; (2) in paragraph (1)— (A) by amending subparagraph (A) to read as follows: (A) an undetectable firearm; or ; and (B) in subparagraph (B), by striking any major component of which, when subjected to inspection by the types of x-ray machines commonly used at airports, does not generate and inserting the following: a major component of a firearm which, if subjected to inspection by the types of detection devices commonly used at airports for security screening, would not generate