In order to attract the provisions of this section, two essential conditions must be fulfilled, viz.; (1) that there should have been a previous conviction under Chapter XII, XVI or XVII, Indian Penal Code, or two previous convictions under the Acts mentioned 516 in clause (b), or three previous convictions within a period of three years under the Acts mentioned in clause (c); and (2) that the authority named should have reason to believe that a person coming within the purview of any of the clauses (a), (b) and (c) is likely again to engage himself in the commission of an offence similar to that for which he had been previously convicted; that is to say, for an offence falling under any of the three chapters mentioned in clause (a), or if he had been twice convicted under the Beggars Act, or the Prevention of Prostitution Act, or thrice convicted under the Prevention of Gambling Act or the Prohibition Act; so that, a previous conviction for "offences relating to coin and Government stamps" has been equated with one for "offences affecting the human body" (chapter XVI) or "offences against property" (chapter XVII) of the Indian Penal Code.