Prosecution for offence against stamp law.

42. The taking of proceedings or the payment of a penalty under this Chapter shall not bar the prosecution of any person who appears to have committed an offence against the stamp law in respect of such instrument :

Provided that no such prosecution shall be instituted in the case of any instrument in respect of which a penalty has been paid unless it appears to the Collector that the offence was committed with an intention of evading payment of the proper duty.