Whoever having been convicted, of an offence under section 39 of this Act, is subsequently convicted of a similar offence under the said section, shall be punishable for every such subsequent offence with double the sentence of imprisonment and fine awarded on previous conviction:
Provided that the enhanced punishment shall not exceed the imprisonment of five years and a fine of three lakhs rupees:
Provided further that the enhanced punishment in any case shall not affect the minimum sentences provided for the offences specified in the first or the second proviso of sub-section (1) of section 39 of this Act.