Section 35. No person shall act, except in the case of a purely amateur match or exhibition, directly or indirectly, as physician, referee, judge, timekeeper, professional boxer or as manager, trainer or second of such a boxer, at a boxing or sparring match or exhibition, or as a matchmaker therefor, unless licensed by the commission upon receipt of such classified fee to be determined annually by the commissioner of administration under the provision of section three B of chapter seven. Whoever, without being so licensed, acts as such manager or engages in the business commonly transacted by managers of boxers shall be punished by a fine of not more than two hundred dollars. For the purposes of sections thirty-two to forty-seven, inclusive, a professional boxer is one who competes for a money prize or teaches or pursues or assists in the practice of boxing as a means of obtaining a livelihood or pecuniary gain. Physicians who desire to officiate without charge at amateur boxing or sparring matches or exhibitions shall be licensed without charge. No person shall be licensed under this section who is under eighteen years of age, except as otherwise provided in section thirty-nine.