Section 128. Any licensee under a license described in section one hundred and twenty-three, and any employee or agent of such a licensee, who violates any provision of said section required to be expressed in the second, fourth, sixth, seventh, eighth, ninth, sixteenth, seventeenth, eighteenth, nineteenth, twentieth or twenty-first condition of said license, and except as provided in section one hundred and twenty-eight A, any person who, without being licensed as hereinbefore provided, sells, rents or leases a firearm, rifle, shotgun or machine gun, or is engaged in business as a gunsmith, shall be punished by a fine of not less than $1,000 nor more than $10,000, or by imprisonment for not less than one year nor more than ten years, or by both such fine and imprisonment.

Evidence that a person sold or attempted to sell a machine gun without being licensed under section one hundred and twenty-three shall, in a prosecution under this section, constitute prima facie evidence that such person is engaged in the business of selling machine guns.