Section 15. Whoever conveys into a correctional institution of the commonwealth or into a jail, house of correction, house of reformation or like place of confinement, a disguise, instrument, tool, weapon or other thing which is adapted or useful to aid a prisoner in making his escape, with intent to aid the escape of a prisoner, or whoever, by any means, aids or assists such prisoner in endeavoring to escape therefrom, whether such escape is effected or attempted or not, and whoever forcibly or fraudulently rescues or attempts to rescue a prisoner held in custody upon a conviction or charge of crime, shall, if the person whose escape or rescue was effected or intended is a convict under sentence to the state prison or is charged with a felony, be punished by a fine of not more than five hundred dollars or by imprisonment in the state prison for not more than ten years; but if he is a convict under sentence to any other of said institutions, by imprisonment in the state prison for not more than seven years; and if he is charged with a misdemeanor, then by a fine of not more than five hundred dollars or by imprisonment in jail for not more than two years.