If any person who has been convicted of any offence punishable under this Act is again guilty of an offence involving a contravention of the same provision, he shall be punishable on a subsequent conviction with imprisonment which may extend to six months, or with fine which may extend to one thousand rupees, or with both:
     Provided that for the purposes of this section no cognizance shall be taken of any conviction made more than two years before the commission of the offence which is being punished.