Section 10A. Any person, other than a federally licensed firearms manufacturer, an authorized agent of the municipal police training committee, or a duly authorized sworn law enforcement officer while acting within the scope of official duties and under the direct authorization of the police chief or his designee, or the colonel of the state police, who sells or keeps for sale, or offers, or gives or disposes of by any means other than submitting to an authorized law enforcement agency, or uses or possesses any instrument, attachment, weapon or appliance for causing the firing of any gun, revolver, pistol or other firearm to be silent or intended to lessen or muffle the noise of the firing of any gun, revolver, pistol or other firearm shall be punished by imprisonment for not more than five years in state prison or for not more than two and one-half years in a jail or house of correction. Nothing contained herein shall be construed to prohibit a federally licensed firearms manufacturer from selling such instrument, attachment, weapon or appliance to authorized law enforcement agencies for law enforcement purposes or to the municipal police training committee for law enforcement training. Upon conviction of a violation of this section, the instrument, attachment or other article shall be confiscated by the commonwealth and forwarded, by the authority of the written order of the court, to the colonel of the state police, who shall destroy said article.